Methods of synthesizing an oxidant and applications thereof

ABSTRACT

Novel methods and devices for synthesizing ferrate and uses thereof are described. One aspect of the invention relates to synthesizing ferrate at a site proximal to the site of use, another aspect of the invention relates to devices and methods for synthesizing ferrate.

RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of the U.S.application Ser. No. 09/905,165, filed Jul. 12, 2001, by Ciampi, andentitled “METHODS OF SYNTHESIZING AN OXIDANT AND APPLICATIONS,” which inturn claims priority to U.S. Provisional Application Serial No.60/218,409, filed Jul. 14, 2000, by Ciampi, and entitled “METHOD ANDSYSTEM FOR TREATING WATER AND SLUDGE WITH FERRATE,” and U.S. ProvisionalApplication Serial No. 60/299,884, filed Jun. 21, 2001, by Ciampi, andentitled “METHODS OF SYNTHESIZING AN OXIDANT AND APPLICATIONS,” all ofwhich are incorporated by reference herein in their entirety, includingany drawings.

FIELD OF THE INVENTION

[0002] The present invention relates, generally, to the manufacture andthe application of the ferrate ion. More particularly, the presentinvention relates to methods and systems for treating, with the ferrateion, solutions containing impurities.

BACKGROUND OF THE INVENTION

[0003] The ferrate ion, FeO₄ ²⁻, is a tetrahedral ion that is believedto be isostructural with chromate, CrO₄ ², and permanganate, MnO₄ ⁻. Theferrate ion has been suggested to exist in aqueous media as thetetrahedral species FeO₄ ²⁻. Redox potentials for FeO₄ ² ion have beenestimated in both acidic and basic media (R. H. Wood, J. Am. Chem. Soc.,Vol. 80, p. 2038-2041 (1957)):

FeO₄ ²⁻+8H⁺+3e ⁻→Fe³⁺+4H₂O E°=2.20V

FeO₄ ²⁻+4H₂O+3e ⁻→Fe³⁺+8OH⁻E°=0.72V

[0004] Ferrate is a strong oxidant that can react with a variety ofinorganic or organic reducing agents and substrates (R. L. Bartzatt, J.Carr, Trans. Met. Chem., Vol. 11 (11), pp. 414-416 (1986); T. J.Audette, J. Quail, and P. Smith, J. Tetr. Lett., Vol. 2, pp. 279-282(1971); D. Darling, V. Kumari, and J. BeMiller, J. Tetr. Lett., Vol. 40,p. 4143 (1972); and R. K. Murmann and H. J. Goff, J. Am. Chem. Soc.,Vol. 93, p. 6058-6065 (1971)). It can, therefore, act as a selectiveoxidant for synthetic organic studies and is capable ofoxidizing/removing a variety of organic and inorganic compounds from,and of destroying many contaminants in, aqueous and non-aqueous media.

[0005] In the absence of a more suitable reductant, ferrate will reactwith water to form ferric ion and molecular oxygen according to thefollowing equation (J. Gump, W. Wagner, and E. Hart, Anal. Chem., Vol.24., p.1497-1498 (1952)).

4FeO₄ ²⁻+10H₂O→4Fe³⁺+20OH⁻+3O₂

[0006] This reaction is of particular interest to water treatmentbecause it provides a suitable mechanism for self-removal of ferratefrom solution. In all oxidation reactions, the final iron product is thenon-toxic ferric ion which forms hydroxide oligomers. Eventuallyflocculation and settling occur which remove suspended particulatematter.

[0007] The use of ferrate may therefore provide a safe, convenient,versatile and cost effective alternative to current approaches forwater, wastewater, and sludge treatment. In this regard, ferrate is anenvironmentally friendly oxidant that represents a viable substitute forother oxidants, particularly chromate and chlorine, which are ofenvironmental concern. Ferric oxide, typically known as rust, is theiron product of oxidation by ferrate. Therefore, ferrate has thedistinction of being an “environmentally safe” oxidant. Although theoxidation reactions with ferrate appear similar to those known for MnO₄⁻ and CrO₄ ²⁻, ferrate exhibits greater functional group selectivitywith higher rate of reactivity in its oxidations and generally reacts toproduce a cleaner reaction product.

[0008] One problem hindering ferrate implementation is difficulty in itspreparation. This difficulty may lead to increased production costs.Moreover, in addition to cost, the current methods known for producing acommercially useful and effective ferrate product, and the results ofthese methods, have been less than satisfactory. There exists a need fornew synthetic preparative procedures that are easier and less expensivein order to provide ferrate material at economically competitive prices.

[0009] Three approaches for ferrate synthesis are known: electrolysis,oxidation of Fe₂O₃ in an alkaline melt, or oxidation of Fe(III) in aconcentrated alkaline solution with a strong oxidant.

[0010] In the laboratory, by means of hypochlorite oxidation of iron(Fe(III)) in strongly alkaline (NaOH) solution, the ferrate product hasbeen precipitated by the addition of saturated KOH (G. Thompson, L.Ockerman, and J. Schreyer, J. Am. Chem. Soc., Vol. 73, pp. 1379-81(1951)):

2Fe³⁺+3OCl⁻+10OH⁻→2FeO₄ ²⁻+3Cl⁻+5H₂O

[0011] The resulting purple solid is stable indefinitely when kept dry.

[0012] Commercial production of ferrate typically uses a syntheticscheme similar to the laboratory preparation, also involving ahypochlorite reaction. Most commonly, using alkaline oxidation ofFe(III), potassium ferrate (K₂FeO₄) is prepared via gaseous chlorineoxidation in caustic soda of ferric hydroxide, involving a hypochloriteintermediate. Another method for ferrate production was described byJohnson in U.S. Pat. No. 5,746,994.

[0013] A number of difficulties are associated with the production offerrate using the method described above. For example, severalrequirements for reagent purity must be ensured for maximized ferrateyield and purity. However, even with these requirements satisfied, thepurity of the potassium ferrate product still varies widely and dependsupon many factors, such as reaction time, temperature, purity ofreagents, and isolation process. Ferrate prepared this way generallycontains impurities, with the major contaminants being alkali metalhydroxides and chlorides and ferric oxide. However, samples of thisdegree of purity are unstable and readily decompose completely intoferric oxides.

[0014] Other than the specific problems with product impurities andinstability, there also exist mechanical problems associated with theisolation of the solid ferrate product, such as filtering cold lyesolutions having a syrupy consistency.

[0015] Other processes for preparation of ferrates are known and used,many of them also involving the reactions with hypochlorite. Forexample, U.S. Pat. No. 5,202,108 to Deininger discloses a process formaking stable, high-purity ferrate(VI) using beta-ferric oxide(beta-Fe₂O₃) and preferably monohydrated beta-ferric oxide(beta-Fe₂O₃.H₂O ), where the unused product stream can be recycled tothe ferrate reactor for production of additional ferrate.

[0016] U.S. Pat. Nos. 4,385,045 and 4,551,326 to Thompson disclose amethod for direct preparation of an alkali metal or alkaline earth metalferrates from inexpensive, readily available starting materials, wherethe iron in the product has a valence of +4 or +6. The method involvesreacting iron oxide with an alkali metal oxide or peroxide in an oxygenfree atmosphere or by reacting elemental iron with an alkali metalperoxide in an oxygen free atmosphere.

[0017] U.S. Pat. No. 4,405,573 to Deininger et al. discloses a processfor making potassium ferrate in large-scale quantities (designed to be acommercial process) by reacting potassium hydroxide, chlorine, and aferric salt in the presence of a ferrate stabilizing compound.

[0018] U.S. Pat. No. 4,500,499 to Kaczur et al. discloses a method forobtaining highly purified alkali metal or alkaline earth metal ferratesalts from a crude ferrate reaction mixture, using both batch andcontinuous modes of operation.

[0019] U.S. Pat. No. 4,304,760 to Mein et al. discloses a method forselectively removing potassium hydroxide from crystallized potassiumferrate by washing it with an aqueous solution of a potassium salt(preferably a phosphate salt to promote the stability of the ferrate inthe solid phase as well as in aqueous solution) and an inorganic acid atan alkaline pH.

[0020] U.S. Pat. No. 2,758,090 to Mills et al. discloses a method ofmaking ferrate, involving a reaction with hypochlorite, as well as amethod of stabilizing the ferrate product so that it can be used as anoxidizing agent.

[0021] U.S. Pat. No. 2,835,553 to Harrison et al. discloses a method,using a heating step, where novel alkali metal ferrates with a valenceof +4 are prepared by reacting the ferrate(III) of an alkali metal withthe oxide (or peroxide) of the same, or a different, alkali metal toyield the corresponding ferrate(IV).

[0022] U.S. Pat. No. 5,284,642 to Evrard et al. discloses thepreparation of alkali or alkaline earth metal ferrates that are stableand industrially usable as oxidizers, and the use of these ferrates forwater treatment by oxidation. Sulfate stabilization is also disclosed.

[0023] The development of an economical source of ferrate is desired toderive the benefits associated with ferrate application in a wide rangeof processes. In view of the difficulties associated with the previouslyknown methods for preparing ferrates and the problems inherent in theferrate produced by these known methods, there is therefore an existingneed for a new preparative method for ferrate that is easy, convenient,safe and inexpensive, and that avoids both the chemical and mechanicalproblems. There also exists a need for a system which reduces orcounteracts the limited stability of ferrate, and systems which employferrate as an environmentally friendly oxidant and disinfectant.

SUMMARY OF THE INVENTION

[0024] A method of continuously synthesizing ferrate is disclosed,comprising mixing a mixture comprising an iron salt and an oxidizingagent in a mixing chamber; delivering at least a portion of the mixtureto a reaction chamber; continuously generating ferrate in the reactionchamber; delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and adding additional ironsalt and oxidizing agent to the mixing chamber.

[0025] Also disclosed is a method of treating, at a site of use, amixture having at least one impurity, comprising continuously generatingferrate in a reaction chamber located proximal to the site of use;contacting the ferrate with the mixture at the site of use, whereby atleast a portion of the impurity is oxidized.

[0026] Also disclosed is a device for continuously synthesizing ferrate,comprising a first holding chamber; a second holding chamber; a mixingchamber controllably connected to the first holding chamber and to thesecond holding chamber, into which a content of the first holdingchamber and a content of a second holding chamber are added to form amixture; a reaction chamber controllably connected to the mixingchamber, into which the mixture is kept for a period of time; and anoutput opening in the reaction chamber through which the mixture may betransported to a proximal site of use.

[0027] Also disclosed is a system for continuously synthesizing ferrate,comprising a first holding chamber containing an iron salt; a secondholding chamber containing an oxidizing agent; a mixing chambercontrollably connected to the first holding chamber and to the secondholding chamber, into which the iron salt and the oxidizing agent arecontrollably added to form a mixture; a reaction chamber controllablyconnected to the mixing chamber, into which the mixture is kept for aperiod of time, and in which ferrate is synthesized, and an outputopening in the reaction chamber through which the ferrate may betransported to a proximal site of use. The “period of time” during whichthe mixture is kept in the reaction chamber may range from seconds tohours to days, but may be any time longer than zero seconds.

[0028] Also disclosed is a method of continuously synthesizing ferrate,comprising providing a mixture of an iron salt and an oxidizing agent;continuously delivering at least a portion of the mixture to a heatingchamber; exposing the mixture to elevated temperatures in the heatingchamber, thereby generating ferrate; removing at least a portion of thegenerated ferrate from the heating chamber; adding additional mixture tothe heating chamber.

[0029] Also disclosed is a device for continuously synthesizing ferrate,comprising a holding chamber; a mover controllably connected to theholding chamber such that at least a portion of a content of the holdingchamber is transferred to the mover; a heating chamber, through which atleast a portion of the mover moves; an output opening in the heatingchamber through which the content on the mover may be transported to aproximal site of use.

[0030] Also disclosed is a device for continuously synthesizing ferrate,comprising a mixing chamber comprising two electrodes, where theelectrodes provide sufficient electric current to convert a solution ofan iron salt to a solution of ferrate; a reaction chamber controllablyconnected to the mixing chamber, into which the mixture is kept for aperiod of time; and an output opening in the reaction chamber throughwhich the mixture may be transported to a proximal site of use. Themixture is kept in the reaction chamber for a period of time longer thanzero seconds.

[0031] Also disclosed is a method of continuously synthesizing ferrate,comprising continuously providing an aqueous solution comprising an ironsalt in a mixing chamber, where the mixing chamber comprises at leasttwo electrodes; providing sufficient electric current to the at leasttwo electrodes to convert at least a portion of the iron salt toferrate; delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and adding additional aqueoussolution to the mixing chamber.

[0032] Also disclosed is a method of synthesizing ferrate, comprisingmixing a mixture comprising an iron salt and an oxidizing agent in amixing chamber; delivering at least a portion of the ferrate to a siteof use that is proximal to the mixing chamber.

BRIEF DESCRIPTION OF THE FIGURES

[0033]FIG. 1 depicts an embodiment of the device for solution phasesynthesis of ferrate ion.

[0034]FIG. 2 depicts an embodiment of the device for solid phasesynthesis of ferrate ion.

[0035]FIG. 3 depicts an embodiment of the device for electrochemicalsynthesis of ferrate ion.

[0036]FIG. 4 is a flow chart depicting some embodiments of the processof generating and purifying ferrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] It is an object of the invention to provide a new, convenient,inexpensive, and safe method for producing a salt of ferrate. Such amethod may produce the sodium salt, but may be used to prepare othersalts of Group I or Group II cations, or other cations, whether metallicor not.

[0038] It is an object of the invention to provide an environmentallyfriendly oxidant for application in a variety of wastewater contaminantsand water treatment problems. Such an oxidant produces a cleanerreaction product(s) and thereby may be used to replace existingenvironmental, laboratory, and industrial oxidants which may havedeleterious side effects or costs.

[0039] It is an object of the invention to provide a new, safe, andinexpensive industrial and environmental remediation chemical oxidantthat overcomes the problems associated with known oxidants for watertreatment (for example, chlorine, hypochlorite, chlorine dioxide,permanganate, and ozone) and the by-products of these oxidants.

[0040] It is an object of this invention to provide a new ferrateproduct to be used in the control of sulfides, including hydrogensulfide gas, in sewer systems, ground water, treatment plants, and wastetreatment facilities.

[0041] It is an object of the invention to provide an improved ferrateproduct for remediation of uranium, transuranics, rocket fuel propellantcontaminants (hydrazine and monomethylhydrazines) and mustard gas.

[0042] It is a further object of the invention to provide an innovativeproduct to be used as coagulant and disinfectant.

[0043] It is an object of the present invention to provide an oxidant tobe used in drinking water disinfection and coagulation, biofoulingcontrol, ground water decontamination, solid surface washing, andhazardous waste treatment.

[0044] It is an object of the present invention to provide an oxidant tobe used in synthetic chemistry.

[0045] It is an object of the present invention to provide an oxidant tobe used in surface preparation, including polymer surface and metallicsurface preparation.

[0046] To achieve at least one of the above-stated objectives, thefollowing methods, manufactures, compositions of matter, and usesthereof are provided.

[0047] I. On-Site Generation

[0048] The inventors have discovered that many of the presentlyunaddressed problems associated with ferrate use relate to thepurification and storage of ferrate. Therefore, in some embodiments ofthe invention, a system of producing ferrate and using it withoutsubstantially further purification, packaging, or preparation isprovided. Because ferrate, in its unpurified form decomposes ratherrapidly, the ferrate produced by the provided methods need not bestored. Ferrate may, and preferably is, used immediately, orsubstantially soon after its generation. Therefore, certain embodimentsof the present invention provide a device that is designed to be locatedin close proximity to the site of use, such that when ferrate isproduced, it may be rapidly and efficiently delivered to the site ofuse, without substantial further purification, packaging, shipping,transfer, or preparation.

[0049] As used herein, the terms “site of generation” or “generationsite” refer to the site where the device for the generation of ferrateis located. In one embodiment exemplified herein, the generation siteincludes a reaction chamber for generation of ferrate. The terms “siteof use,” “use site,” or “treatment site” refer to the site where theferrate is contacted with the object it is to oxidize, synthesize,disinfect, clean, plate, encapsulate, or coagulate.

[0050] The terms “close proximity” and “proximal” are usedinterchangeably herein. These terms are used to refer to the relativelocations of the generation site and the use site when the two sites arewithin a distance that allows for the ferrate to travel the distancewithin a half-life of its decomposition. “Half-life” of a decompositionis understood to be the amount of time it takes for one half of thematerial present to undergo decomposition. The half-life for any givenferrate composition will depend on the conditions under which theferrate is generated and/or stored. Thus, for example, the temperature,concentration of base, concentration of oxidizing agent and presence ofimpurities will all tend to affect the half-life of the ferratecomposition. However, the half-life can be readily measured by thosehaving ordinary skill in the art using conventional techniques.Therefore, a generation site is “proximal” to a use site when theconcentration of ferrate at the use site at the time of delivery isequal to or greater than one-half of the concentration of ferrate at thegeneration site. The distance between the generation site and the usesite is defined in terms of the half-life and a length of time requiredfor delivery, rather than simply in terms of physical displacement.Thus, the physical displacement between a generation site and use sitethat are in close proximity may vary depending on the half-life of theferrate composition being delivered between the two sites and the rateat which the composition is delivered. Accordingly factors affectingboth the rate of ferrate transfer and factors affecting the half-lifewill all affect the maximum physical displacement permissible for thetwo sites to remain in close proximity. Factors affecting the rate offerrate transfer include, but are not limited to, the pressure generatedby a pump used in the transfer and the size of the plumbing used in thetransfer.

[0051] The on-site generation methods provide a number of advantagesover known processes. Initially, because the produced ferrate can beused without further substantial purification or stabilization, there isno need for storage or shipping. In addition, eliminating the need for ahighly purified ferrate ultimately saves costs by increasing the yieldof the reaction because less starting materials are needed to afford thesame amount of usable ferrate.

[0052] The current practice for making and purifying ferrate involvesthe production of sodium ferrate using sodium hydroxide, followed by theprecipitation of potassium ferrate using potassium hydroxide. Thus, thecurrent methods use base in two distinct steps. The methods of some ofthe embodiments of the present invention require substantially less baseto produce usable ferrate since the methods do not require the additionof potassium hydroxide to sodium ferrate.

[0053] Thus, the ferrate produced by some of the methods of the presentinvention can be used or purified in a solution-to-solution phasemanner, i.e., ferrate is generated in the solution phase and is used inthe solution phase, without the intervening crystallization, orconversion to the solid phase (i.e., solution-to-solid phase). Ifpartial purification or separation is required, then such purificationor separation can be achieved in the solution phase as well. In certainembodiments of the present invention, the produced ferrate is notconverted to any phase other than the solution phase.

[0054] The solution-to-solution phase concept discussed above providesadvantages over the solution-to-solid phase method. For example, asdiscussed above, conversion to solid or crystallization is limited bythe nature of the counter-ion. Crystallization of potassium ferrate isless difficult than crystallization of sodium ferrate. Ferrate withcertain counter-ions can never be crystallized or can be crystallizedunder very difficult conditions. Using the solution-to-solution phaseconcept, virtually any counter-ion can be used. In addition, onceferrate is crystallized, it would have to be re-dissolved in aqueousmedia for use. The re-dissolution of ferrate adds both cost (loss offerrate, addition of water, and dissolution tanks, to name a few) andtime (dissolution time) to the process. In the solution-to-solutionphase method, ferrate is already in aqueous solution and can be used assuch. Furthermore, if pH is to be adjusted, it is more efficient toadjust the pH of the ferrate stream once it is produced than to adjustthe pH of a ferrate solution prepared from adding solid ferrate towater. Yet another advantage of the solution-to-solution phase conceptis the ease of production of custom blends.

[0055] The above advantages result in the entire process being cheaperand more economical than the available processes. The relatively lowcost of production allows the ferrate to be used in a large variety ofsettings, which heretofore have been substantially unavailable for theoxidizing benefits of the compound due to its cost. Most importantly,ferrate may now be made available to municipal water and wastewatertreatment facilities, which are cost conscious.

[0056] Furthermore, on-site generation of ferrate allows the end user tocontrol the amount of ferrate to be produced. This may alleviate orreduce the need for inventory control of ferrate, in addition toalleviating or reducing the need to store ferrate.

[0057] II. Process for Preparing Ferrate

[0058] A. Solution Phase Production

[0059] In one aspect, the invention relates to a method of continuouslysynthesizing ferrate, comprising mixing an iron salt and an oxidizingagent in a mixing chamber to form a mixture; delivering at least aportion of the mixture to a reaction chamber; continuously generatingferrate in the reaction chamber; delivering at least a portion of theferrate to a site of use that is proximal to the reaction chamber; andadding additional iron salt and oxidizing agent to the mixing chamber.

[0060] In certain embodiments, the above method further comprises theaddition of a solvent during the mixing step. In some embodiments, thesolvent is water and the mixture is, therefore, an aqueous solution. Inother embodiments, the mixture is a non-aqueous solution. In certainother embodiments, the oxidizing agent may be a neat liquid, in whichcase it would act as a solvent for dissolving the iron salt as well. Instill other embodiments, the iron salt and the oxidizing agent are addedas solids, and the reaction takes place in solid form.

[0061] Thus, one embodiment of the invention relates to a method ofcontinuously synthesizing ferrate, comprising mixing an aqueous solutioncomprising an iron salt and an oxidizing agent in a mixing chamber;delivering at least a portion of the aqueous solution to a reactionchamber; continuously generating ferrate in the reaction chamber;delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and adding additional aqueous solutionto the mixing chamber.

[0062] It is known to those of skill in the art that iron canaccommodate an oxidation state in the range of 0 to +8, including the+1, +2, +3, +4, +5, +6, and +7 oxidation states. Iron in the 0 oxidationstate is elemental iron. Most compounds and salts of iron found innature have an oxidation state of either +2 (Fe(II)) or +3 (Fe(III)). Inthe context of the present invention, “ferrate” refers to an ioncomprising iron in its +4, +5, +6, +7, or +8 oxidation states, i.e.,comprising Fe(IV), Fe(V), Fe(VI), Fe(VII), or Fe(VIII). The ferrate ionalso contains oxygen atoms. It may or may not comprise atoms of otherelements. Furthermore, “ferrate” may also refer to a mixture of ionscomprising iron in various oxidation states, as long as at least aportion of the ions comprise iron exhibiting an oxidation state of +4 orhigher. Thus, for example, ferrate refers to a FeO₄ ²⁻, where the ironis Fe(VI) and the other atoms in the ion are oxygen atoms. A solutioncomprising FeO₄ ²⁻ ions may also contain ions exhibiting iron in its +5oxidation state, or any other oxidation state, including the elementalform of iron, and it would still be called ferrate. Similarly, a ferratesolution may contain no Fe(VI) containing ions. A ferrate solution mayalso comprise Fe(V) or Fe(IV) containing ions. Therefore, any ioncomprising Fe(IV), or higher oxidation state iron atoms, and at leastone oxygen atom is considered to be “ferrate.” Ferrate ions may beeither cations or anions.

[0063] It is understood by those skilled in the art that any ionrequires a counterion of equal, though opposite, charge. This is alsotrue for the ferrate ions of the present invention. The counterion maybe any ion that renders neutral the overall charge of the mixturecomprising the ferrate ion. When ferrate is an anion, the counterion maybe any cation. The most common form of ferrate to-date is K₂FeO₄, wherethe iron is in its +6 oxidation state, the ferrate is an anion and thecounterion is potassium. Any other counter-cation, such as, and withoutlimitation, sodium, calcium, magnesium, silver, etc., may also bepresent.

[0064] By “continuously generating” or “continuously synthesizing” it ismeant that once ferrate begins to be delivered to the reaction chamber,there continues to be an amount of ferrate in the reaction chamber forthe duration of time that the method is being practiced. Thus, asdescribed hereinbelow in greater detail, in one embodiment of acontinuous generation process in accordance with the present invention,there is a constant flow of material from the mixing chamber to thereaction chamber. In other embodiments, as also described hereinbelow,material is intermittantly transferred from the mixing chamber to thereaction chamber while maintaining at least some ferrate in the reactionchamber.

[0065] In certain embodiments, the additional mixture of iron salt andoxidizing agent of the above method is added in an amount tosubstantially replace the portion of the mixture delivered to thereaction chamber. In the context of the present invention, for a secondamount to substantially replace a first amount, the second amount may beless than, equal to, or greater than the first amount.

[0066] In certain embodiments, the method of producing ferrate furthercomprises adding a base to the mixture. The base may comprise a nitrogenbase or an ion selected from the group consisting of hydroxide, oxide,sulfonate, sulfate, sulfite, hydrosulfide, phosphate, acetate,bicarbonate, and carbonate, or a combination thereof. “Nitrogen bases”are selected from acyclic and cyclic amines. Examples of nitrogen basesinclude, but are not limited to, ammonia, amide, methylamine,methylamide, trimethylamine, trimethylamide, triethylamine,triethylamide, aniline, pyrrolidine, piperidine, and pyridine, or saltsthereof.

[0067] To produce ferrate by the methods of the present invention, aniron salt must be provided. “Iron salt” or “salt of iron” refers to acompound that comprises an iron atom in an oxidation state other thanzero. The iron salt used by the methods of the present invention may beproduced in situ, i.e., by oxidizing elemental iron either chemically orelectrochemically prior to its introduction into the mixing chamber orby performing the oxidation inside the mixing chamber. The iron atom inthe iron salt will have an oxidation state greater than zero, preferably+2 or +3, though this oxidation state may be reached transiently as theiron atom is converted from its starting oxidation state to the finaloxidation state of +4 or above.

[0068] In certain embodiments, the iron salt may be selected from thegroup consisting of ferric nitrate, ferrous nitrate, ferric chloride,ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate,ferrous sulfate, ferric phosphate, ferrous phosphate, ferric hydroxide,ferrous hydroxide, ferric oxides, ferrous oxides, ferric hydrogencarbonate, ferrous hydrogen carbonate, ferric carbonate, and ferrouscarbonate, or a combination thereof. All different forms of ferric andferrous oxide are contemplated to be used with the methods of thepresent invention.

[0069] In some embodiments of the present invention, ferrate is producedby chemical oxidation of the iron salt. The chemical oxidation isperformed by mixing an oxidizing agent, or a solution containing theoxidizing agent, with the iron salt, or with the solution containing theiron salt. In some embodiments, the oxidizing agent, or a solutioncontaining the oxidizing agent, is added to the iron salt, or to thesolution containing the iron salt, whereas in other embodiments, theiron salt, or the solution containing the iron salt, is added to theoxidizing agent, or to a solution containing the oxidizing agent. An“oxidizing agent” is a chemical compound that oxidizes another compound,and itself is reduced. In certain embodiments, the oxidizing agentcomprises at least one of the following: a hypohalite ion, a halite ion,a halate ion, a perhalate ion, ozone, oxone, halogen, a peroxide, asuperoxide, a peracid, a salt of a peracid, and Caro's acid, or acombination thereof.

[0070] Embodiments of the invention include those in which the oxidizingagent comprises a hypohalite ion selected from the group consisting ofthe hypochlorite ion, the hypobromite ion, and the hypoiodite ion. Inother embodiments of the invention, the oxidizing agent comprises ahalite ion selected from the group consisting of the chlorite ion, thebromite ion, and the iodite ion. In yet other embodiments of theinvention, the oxidizing agent comprises a halate ion selected from thegroup consisting of the chlorate ion, the bromate ion, and the iodateion. Certain other embodiments of the invention include those in whichthe oxidizing agent comprises a perhalate ion selected from the groupconsisting of the perchlorate ion, the perbromate ion, and the periodateion.

[0071] Thus, in an embodiment of the present invention, an aqueoussolution of an iron salt and an oxidizing agent is mixed in a mixingchamber. A base, or a combination of bases, may also be added to themixing chamber at this time. The solution is mixed in the mixing chamberfor a certain period of time, which may range from seconds to hoursdepending on the conditions of the mixing, e.g., the temperature or theconcentration of the ingredients. Those skilled in the art recognizethat at this stage ferrate production begins.

[0072] As the mixing is taking place, at least a portion of the mixtureis delivered to a reaction chamber. The mixture is held in the reactionchamber for a certain period of time until the amount of ferrate in themixture, e.g., the concentration of ferrate in an aqueous solution,reaches a pre-determined level. The concentration of ferrate for use isdetermined based on the need for the ferrate and the conditions for thesynthesis or use. Certain applications may require higher yields offerrate than others. Therefore, the time that mixture remains in thereaction chamber may range from seconds to hours. The reaction chambermay also be used as a “holding tank,” i.e., a place to keep thegenerated ferrate, at a certain temperature, to be used at a later time.The holding tank may be at room temperature, or at a temperature that iseither higher or lower than room temperature. The mixture containing theferrate is then removed from the reaction chamber and is delivered tothe site of use. The site of use is “proximal” to the reaction chamber.

[0073] In certain embodiments, as the mixture is removed from the mixingchamber to the reaction chamber, additional iron salt and oxidizingagent is added to the mixing chamber. In other embodiments, additionaliron salt and oxidizing agent is added to the mixing chamber after allof the mixture within the mixing chamber has been transferred to thereaction chamber. It is contemplated in some of the embodiments of thepresent invention that the flow of the mixture from the mixing chamberto the reaction chamber is continuous. Therefore, while ferrate isneeded, new batches of the mixture are to be added to the mixingchamber.

[0074] In some of the embodiments of the present invention, in additionto the iron salt, a metal oxide is added to the mixture. The metal oxidemay be added at any point during the production of ferrate, either as anoriginal ingredient, or in the mixing chamber, or in the reactionchamber, or anywhere along the path. The metal oxide may also be addedto a mixture comprising ferrate subsequent to the production of ferrate,when ferrate is being contacted, or after ferrate has been contacted,with the object to be synthesized, cleaned, disinfected, oxidized, orcoagulated. The metal atom of the metal oxide may be a main group metal,a transition metal, or an f-block metal. A “transition metal” is a metalwithin columns 3-12 of the periodic table, i.e., metals in the scandium,titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper,and zinc triads. An “f-block metal” is a metal in the lanthamide oractinide series, i.e., metals with atomic numbers 57-71 and 89-103.Thus, lanthanum and actinium are both transition metals and f-blockmetals. The metal oxide may be scandium oxide, titanium oxide, vanadiumoxide, manganese oxide, cobalt oxide, nickel oxide, copper oxide, zincoxide, gallium oxide, yttrium oxide, zirconium oxide, niobium oxide,molybdenum oxide, ruthenium oxide, rhodium oxide, palladium oxide,silver oxide, cadmium oxide, indium oxide, tin oxide, hafnium oxide,tantalum oxide, tungsten oxide, rhenium oxide, osmium oxide, iridiumoxide, platinum oxide, or any salt containing the oxides of thesemetals.

[0075] In certain embodiments, the solution comprising ferrate isirradiated with light before or during use. In other embodiments, thesolution comprising ferrate is kept in the dark before use. When thesolution is irradiated with light, the light may be a light of anyfrequency within the electromagnetic spectrum, i.e., anywhere betweenradio waves and x-rays and gamma radiation, including ultraviolet light,visible light, or infrared light.

[0076] Certain other embodiments of the present invention are directedto a “batch process,” during which ferrate is generated once. Thus,these embodiments of the present invention are directed to a method ofsynthesizing ferrate, comprising adding an aqueous solution comprisingan iron salt and an oxidizing agent in a mixing chamber; mixing theaqueous solution; delivering at least a portion of the aqueous solutionto a reaction chamber; and delivering at least a portion of the ferrateto a site of use that is proximal to the reaction chamber.

[0077] In certain embodiments, the ferrate generated by the above methodin the mixing chamber is delivered to the site of use without beingdelivered to a separate reaction chamber. In these embodiments,therefore, the mixing chamber and the reaction chamber are one and thesame. In certain other embodiments, after the mixing in the mixingchamber, the ferrate solution is delivered to a holding tank where it iskept until its use is needed. In any event, the ferrate solution is heldfor a period of time that is less than or equal to the half-life of theferrate in the solution under the conditions (i.e., temperature,concentration, pH, etc.) it is held.

[0078] B. Solid State Production

[0079] In another aspect, the invention relates to a method ofcontinuously synthesizing ferrate, comprising providing a mixture of aniron salt and an oxidizing agent; continuously delivering at least aportion of the mixture to a heating chamber; exposing the mixture toelevated temperatures in the heating chamber, thereby generatingferrate; removing at least a portion of the generated ferrate from theheating chamber; adding additional mixture to the heating chamber.

[0080] In certain embodiments, the exposure of the mixture to elevatedtemperatures and the removal of ferrate from the exposure is continuous.

[0081] In some embodiments, the additional mixture added to the heatingchamber is in an amount to substantially replace the portion of theferrate removed from the heating chamber.

[0082] By “continuously delivering” it is meant that once the mixture ofiron salt and oxidizing agent begins to be delivered to the heatingchamber, it continues to be delivered to the heating chamber for theduration of time that the method is being practiced.

[0083] In certain embodiments of the invention, a base, as describedherein, is also added to the mixture.

[0084] In some of the embodiments of the present invention, the mixtureof the iron salt and the oxidizing agent is carried through the heatingchamber on a belt. The belt is made of materials that can withstandtemperatures higher than room temperature. These materials may include,but not be limited to, rubber, steel, aluminum, glass, porcelain, etc.

[0085] In certain embodiments of the invention the mixture is poureddirectly onto the belt, whereas in other embodiments, the mixture ispoured into containers and the containers are placed on the belt. In anyof these embodiments, the surface that comes to contact with the mixtureis not reactive towards ferrate or other oxidants.

[0086] The heating chamber is heated to temperatures higher than roomtemperature. “Room temperature” is about 20° C. In some embodiments theheating chamber is heated to a temperature of between about 20° C. andabout 1000° C., or between about 50° C. to about 500° C., or betweenabout 100° C. to about 400° C. By “about” a certain temperature it ismeant that the temperature range is within 40° C. of the listedtemperature, or within 30° C. of the listed temperature, or within 20°C. of the listed temperature, or within 10° C. of the listedtemperature, or within 5° C. of the listed temperature, or within 2° C.of the listed temperature. Therefore, by way of example only, by “about400° C.” it is meant that the temperature range is 400±40° C. in someembodiments, 400±30° C. in some embodiments, 400±20° C. in someembodiments, 400±10° C. in some embodiments, or 400±5° C. in otherembodiments, or 400±2° C. in still other embodiments. In someembodiments the temperature remains relatively constant throughout theprocess whereas in other embodiments the temperature varies during theprocess. In the embodiments where the temperature varies, thetemperature may be ramped up, i.e., the final temperature is higher thanthe initial temperature, or ramped down, i.e., the final temperature islower than the initial temperature.

[0087] Thus, in some embodiments of the present invention, a mixture ofan iron salt and an oxidizing agent is put on a belt. The iron salt andthe oxidizing agent may be pre-mixed prior to addition to the belt, orthey may be mixed subsequent to addition to the belt. The mixture may beadded directly onto the belt or may be added to containers that areplaced on the belt. The mixture may be added to the containers beforethe containers are put on the belt or the mixture may be added to thecontainers while the containers are on the belt. In certain embodiments,base is also added to the mixture at some point.

[0088] The belt then moves through a heating chamber, thereby heatingthe mixture. The heat must be sufficient to produce ferrate in themixture. The speed of the belt through the heating chamber, the lengthof time the mixture is heated, and the temperature to which the mixtureis heated are all adjustable. Thus, the mixture may be heated forseconds or for hours.

[0089] Subsequent to the heating event, the heated mixture, nowcomprising ferrate, is removed from the belt. The belt then returns tothe original location for the addition of more of the mixture. It iscontemplated that the movement of the belt through the heating chamberis continuous.

[0090] In some embodiments, the mixture exposed to elevated temperaturein the above method is a solid.

[0091] C. Electrochemical Production

[0092] In another aspect, the invention relates to a method ofcontinuously synthesizing ferrate, comprising providing an aqueoussolution comprising an iron salt in a reaction chamber, where thereaction chamber comprises at least two electrodes; providing sufficientelectric current to the at least two electrodes to convert at least aportion of the iron salt to ferrate; continuously delivering at least aportion of the ferrate to a site of use that is proximal to the reactionchamber; and adding additional aqueous solution to the reaction chamberto substantially replace the portion of the aqueous solution deliveredto the holding chamber.

[0093] By “continuously delivering” it is meant that once ferrate beginsto be delivered to the site of use, it continues to be delivered to thesite of use for the duration of time that the method is being practiced.

[0094] In certain embodiments of the invention, base is added to theaqueous solution, while in other embodiments, acid is added.

[0095] The reaction chamber comprises two electrodes. The electrodes aredesigned to conduct electricity through the aqueous solution, therebyconverting the iron of the iron salt to ferrate in an electrochemicalreaction. The iron of the iron salt may have been added to the solutionas an iron salt, or may be the dissolved iron electrode, which becamedissolved upon the introduction of electricity. It is contemplated thatas solution containing ferrate is removed from the reaction chamber,additional aqueous solution is added to the mixing chamber foradditional reactions. In certain embodiments, the flow of materials fromthe reaction chamber to the holding chamber is continuous.

[0096] D. Other Examples of Methods of Ferrate Production

[0097] In one embodiment, ferric sulfate particles may be added to astatic mixer and mixed in an aqueous medium. The static mixer includes amixing mechanism that is capable of microparticulating particles. Staticmixers may be continuous radial mixing devices, characterized by plugflow or any other conventional mixer. Static mixers are preferred inthat they have short residence times and little back mixing. Thus,proper dosing of feed components with no fluctuation in time is aprerequisite for good performance.

[0098] Another desirable feature of static mixers is that they have nomoving parts for mixing. The absence of moving parts and reliance onsurface area and conformation for reactant/product movement reduces theneed for coolant to cool the reaction. Thus, static mixers arecomparatively low maintenance pieces of equipment. The static mixersused in the processes of the present invention may be incorporated intopump-around loop reactors or in cascade type reactors, such as thosemanufactured by Koch, i.e., The Koch-SMVP packing /Rog 92/. Other staticmixers include Koch type SMF, SMXL-R, SMXL, SMX and SMV type.

[0099] For other embodiments, a micro reactor is used for mixingreactants. Micro-reactors and static mixers are usable to make ferratein a continuous process or a semi-continuous process.

[0100] The mixing mechanism may be a tortuous path, a mixing device oran aspirator. Oxone or Caro's Acid or other strong oxidant in containeris added to the static mixer. The term “oxone” as used herein refers topotassium peroxymonopersulfate or potassium monopersulfate. Reactionbegins instantaneously and generates heat. The temperature of thereaction is adjusted through the use of a cooling coil or cooling jacketto a temperature of about −10° C. Temperature is controlled through afeed forward feed back control mechanism. Water is employed as atransport medium for transporting the ferric sulfate, oxidant andreaction products. The volume of the water is minimized to a volume thatmaximizes ferrate production yield.

[0101] An amount of dry KOH may be added that is effective to maximizeferrate production. The KOH is added to another micro mixer or staticmixer KOH is added to a main reactor. The KOH is cooled to about −10° C.prior to introduction to the main reactor. The main reactor is also astatic mixer.

[0102] An excess of KOH prevents conversion of Fe(III) to ferrate. Theuse of static mixers maximize surface area available for reaction forall of the reactants. It is believed that the use of a static mixer ormicro mixer speeds up the reaction process.

[0103] A use of Caro's acid is preferred in that it aids in stabilizingferrate because sulfate from the Caro's acid “buffers” the ferrate. Itis understood, however, that if the static mixer is positioned proximalto water or wastewater to be treated, sulfate stabilization is optionaland Fe(0) oxidation can occur with another oxidant, such as chlorine orperoxide.

[0104] The temperature in the reactor is preferably maintained at about40° C., but may be as low as 20° C. or as high as 60° C. As products areremoved from the reactor, the temperature in the product stream isgradually decreased to room temperature.

[0105] A use of a static mixer permits a method of water treatment thatincludes shocking an iron moiety with an oxidant, quenching the reactionwith KOH and injecting the ferrate into a water or wastewater or sludgestream. The use of a static mixer renders a complex chemical reactionperformable by operators of water and waster treatment plants. Becauseof the microparticulation of iron species and very rapid mixing,conventional concerns about temperature control are substantiallyeliminated.

[0106] In one other embodiment ferrate is produced in a continuousprocess by hypochlorite oxidation of iron (III) in a strongly alkalinesolution and is precipitated by the addition of saturated KOH.Hypochlorite used in ferrate synthesis is formed by disproportionationof chlorine in a cold caustic soda solution:

Cl₂+OH⁻→Cl⁻+OCl⁻+H⁺.

[0107] Ferrate ion may be produced by adding a material such as ferricnitrate to the hypochlorite solution described:

10OH⁻+3OCl⁻+2Fe³⁺→2FeO₄ ²⁻+3Cl⁻+5H₂O

[0108] Synthesis of ferrate begins by addition of KOH solutions to acold-water jacketed reactor set between 20° C. and 40° C. Gaseous orliquid chlorine is bubbled through the liquid reaction mixture, and thesolid iron salt or oxide is added. Atmospheric pressure is maintained inthe reactor. The ranges of mole ratios of reactants, Cl₂, KOH, Fe(III),are 1.5-30:10-60:1. The smaller ratios decrease product yields, whilethe larger ratios require larger recycle streams back to the reactor,leave KOH unused, or accelerate ferrate decomposition.

[0109] The average residence time of the ferrate in the reactor is 180minutes. Residence times greater than 30 minutes lead to significantferrate decomposition. The product mixture leaving the reactor istypically 2-6% potassium ferrate by weight.

[0110] The reaction mixture includes solid K₂FeO₄, KCl, and Fe(OH)₃ andaqueous KOH, KOCl, KCl, and a small amount of K₂FeO₄. The KOHconcentration in this mixture is increased to 35-45% by weight tofurther precipitate the ferrate from solution. The temperature islowered during this process to 5-20° C. to maximize the yield of solidpotassium ferrate. The crude solid product is separated bycentrifugation within 5 minutes of finishing the KOH addition and theliquids are recycled back to the reactor.

[0111] The crude product is contaminated with KCl and Fe(OH)₃.Selectively dissolving the potassium ferrate into 10-20% KOH (aq), byweight, at 20-50° C., purifies the product. The KCl and Fe(OH)₃ areinsoluble in this media and are removed by centrifugation. The solidsmay be separated and reprocessed for use as starting materials inferrate production.

[0112] The ferrate ion may be reprecipitated by addition ofconcentration KOH solutions, 40-55% by weight, or solid KOH. When theresulting mixture is 30%, crystals of K₂FeO₄ precipitate when thesolution is cooled to between −20 and 0° C. As in the earlier separationsteps, the solid is collected by centrifugation. The separated KOHsolutions may be recycled to the ferrate reactor.

[0113] The potassium ferrate produced may be washed in a tank withanhydrous DMSO to remove any entrapped KOH or water. The DMSO isrecovered by flash evaporation. Next, the solid is transferred to amethanol wash tank for further purification. The solid is finallycollected by centrifugation. The methanol is recovered by distillation.

[0114] In another embodiment reactants described above are added to areactor cooled to a temperature of 20° C. After about 180 minutes,reaction products are treated with KOH, to solubilize any precipitatedferrate and the entire mixture is transferred to water or wastewater orsludge for treatment. For one embodiment, effluent from the reactorincludes unreacted ferric sulfate, unreacted oxone, potassium sulfate,KOH and about 20% dissolved ferrate. The presence of KOH and ferric ionsretard the decomposition rate with water as the product stream is beingmixed with untreated water.

[0115] The mixture containing the ferrate may be polished, if required.

[0116] In another embodiment hypochlorite is substituted for chlorinegas. By introducing NaCl to the reaction mixture, Na₂FeO₄ isprecipitated without any need for a KOH leaching step or extraequipment.

[0117] In another embodiment ferrate is generated as a solid in afluidized bed reaction. The fluidized bed comprises one or more ofFeCl₂, FeSO₄, Fe₂(SO₄)₃, Fe(NO₃)₃ and beta-ferric oxide monohydrate,oxygen gas and chlorine gas. The reaction occurs at a reducedtemperature, such as 20° C. Crystals of ferrate are produced.

[0118] In one other embodiment ferrate is produced as a result of adirect reaction of alkali peroxides, such as sodium peroxide orpotassium peroxide or potassium superoxide with hematite to producepotassium or sodium ferrate. The reaction is believed to proceed bythese chemical reactions: Mole ratio Fe₂O₃ + 6 KO₂ → 2 K₂FeO₄ + K₂O + 3O₂(g) 1 Fe₂O₃:6 K₂O Fe₂O₃ + 3 K₂FeO₄ + K₂O 1 Fe₂O₃:3 K₂O₂ 1 Fe:3 K, forboth

[0119] The temperature of reaction for this synthetic approach is about400 to 600° C. for a time of about 12 hours. It is believed thatchemical reaction occurs though a solid-solid contact, a liquid-solidcontact or a vapor/solid contact. The liquid is a molten salt. The vaporis a material such as K₂O₂ vapor.

[0120] Reactants should be dry, of fine particle size and well mixed.Mixing should avoid contact with air, as moisture and CO₂ will reactwith peroxide. Reactants should be held at 120 to 150° C. in a TGA indry nitrogen to thoroughly remove any adsorbed water prior to heating tothe TGA reaction temperature.

[0121] When dissolved peroxide/superoxide reacts with hematite, itproduces ferrate, dissolved in a salt solution. Upon cooling, thedissolved ferrate ions precipitate from the salt as crystals of K₂FeO₄.A high temperature route produces K₂FeO₄, but with modest yields andwith a requirement of a subsequent processing step to separate theK₂FeO₄ from the salt mixture. In one embodiment, the salt mixture is notseparated and the entire mixture is used for water or wastewatertreatment. One advantage is that a simple process involving a singlehigh temperature reactor translates into a lower cost of production.

[0122] One other option is a two-step process. An inexpensive source ofperoxide/superoxide is processed in a first reactor to produce a gasstream containing peroxide/super oxide species. The gas stream is ductedinto a second reactor containing hematite, where a direct reaction iscarried out to produce ferrate. The temperatures of reactors A and B areseparately set to optimize respective processes. With this process, thefirst reactor temperature is about 1000° C. and the second reactortemperature is 400-500° C. The peroxide reaction may be performed in astatic mixer as described for a reaction of iron and Caro's acid.

[0123] While oxidants of oxone, Caro's acid, peroxide/superoxide,chlorine and hypochlorite are described herein, it is understood thatother oxidants may be suitable for use. Some of these oxidants aredescribed in an article on ferrate oxidants in Grazzino Italiano byLosanna. It is believed that enzymes may also be usable in ferrateprocess embodiments of the present invention to reduce reactiontemperature.

[0124] III. Device for On-Site Generation of Ferrate

[0125] A. Solution Phase Production Device

[0126] In another aspect, the invention relates to a device forcontinuously synthesizing ferrate for delivery to a site of use,comprising a first holding chamber; a second holding chamber; a mixingchamber controllably connected to the first holding chamber and to thesecond holding chamber, into which a content of the first holdingchamber and a content of a second holding chamber are added to form afirst mixture; a reaction chamber controllably connected to the mixingchamber, the reaction chamber adapted to receive the first mixture andmaintain the first mixture for a period of time; a ferrate mixture inthe reaction chamber; and an output opening in the reaction chamberthrough which the ferrate mixture is adapted to be transported to thesite of use, where the site of use is proximal to the reaction chamber.

[0127] In some embodiments the mixing chamber further comprises amechanical agitator.

[0128] In other embodiments, the mixing chamber comprises a tubeconfigured to mix the mixture as it passes through the tube.

[0129] Certain embodiments of the invention relate to a device in whichthe mixing chamber further comprises a temperature control device. Thetemperature control device may include a jacket around the mixingchamber whereby a cooled or heated fluid is passed through the jacket inorder to maintain the temperature of the intraluminal space at a certainpredetermined level.

[0130] Other embodiments of the invention further comprise a pumpdownstream from the first and the second holding chambers and upstreamfrom the mixing chamber. The pump controls the flow of materials intothe mixing chamber.

[0131] Some other embodiments of the invention further comprise a pumpdownstream from the mixing chamber and upstream from the reactionchamber. This pump controls the flow of material out of the mixingchamber and into the reaction chamber.

[0132] In some of the embodiments of the invention the reaction chambercomprises a tube located between the mixing chamber and the outputopening.

[0133] In another aspect the invention relates to a system forcontinuously synthesizing ferrate, comprising a first holding chambercontaining an iron salt; a second holding chamber containing anoxidizing agent; a mixing chamber controllably connected to the firstholding chamber and to the second holding chamber, into which the ironsalt and the oxidizing agent are controllably added to form a mixture; areaction chamber controllably connected to the mixing chamber, intowhich the mixture is kept for a period of time, and in which ferrate issynthesized, and an output opening in the reaction chamber through whichthe ferrate may be transported to a proximal site of use.

[0134] In some embodiments a base, as described herein, is added to themixture. The iron salt, the oxidizing agent, the mixing chamber, and thereaction chamber are as described herein.

[0135] In certain embodiments, the device of the invention furthercomprises a pump downstream from the first and the second holdingchambers and upstream from the mixing chamber. In other embodiments, thedevice further comprises a pump downstream from the mixing chamber andupstream from the reaction chamber.

[0136]FIG. 1 shows an embodiment of the solution state productiondevice. The figure depicts two holding chambers 101. Other embodimentsof the invention may exhibit additional holding chambers, depending onthe number of ingredients added initially. Some embodiments of theinvention may exhibit only one holding chamber 101. The holding chambersare connected to the mixing chamber 103. In some embodiments, the flowof material between the holding chambers 101 and the mixing chamber 103may be controlled. The flow is controlled either by the presence of apump or a valve (107) after each holding chamber 101, or by the presenceof a pump or a valve (109) before the mixing chamber 103, or by acombination thereof. In certain embodiments, no pump or valve existsbetween the holding chamber 101 and the mixing chamber 103.

[0137] The mixing chamber 103 is connected to the reaction chamber 105.In some embodiments, the flow of material between the mixing chamber 103and the reaction chamber 105 may be controlled. The flow may becontrolled by the presence of a pump or a valve (111) after the mixingchamber 103. In certain embodiments, no pump or valve exists between themixing chamber 103 and the reaction chamber 105.

[0138] The reaction chamber 105 is connected with an output opening 115,through which the product of the reaction is transferred to the site ofuse. The flow from the reaction chamber 105 to the output opening 115may be controlled. The control may be through the use of a pump or avalve (113). In certain embodiments, no pump or valve exists between thereaction chamber 105 and the output opening 115.

[0139] As depicted in FIG. 1A, in certain embodiments, the holdingchambers 101 connect to the mixing chamber 103 via a single pipe, i.e.,there is a T-junction before the mixing chamber 103. However, asdepicted in FIG. 1B, in certain other embodiments, each holding chamber101 is separately connected to the mixing chamber 103.

[0140] In some embodiments, the device of the present invention alsofeatures a temperature control unit. The temperature control unitcontrols the temperature of the holding chambers 101, the mixing chamber103, the reaction chamber 105, or a combination thereof, or thetemperature of the entire device. These components may be held at roomtemperature, at a temperature above room temperature, or at atemperature below room temperature, depending on the reaction conditionsand the needs of the particular use contemplated. In some embodiments,different parts of the device are held at different temperatures, thus,requiring more than one temperature control unit for the device.

[0141] In certain embodiments, the mixing chamber 103 may just be a pipeor a hose connecting the holding chambers 101 to the reaction chamber105. In some other embodiments, the reaction chamber 105 may just be apipe or a hose connecting the mixing chamber 103 to the output opening115. Therefore, in one embodiment of the invention, the entire devicewill comprise of a pipe or a hose connecting the holding chambers 101 tothe output opening 115.

[0142] B. Solid State Production Device

[0143] In another aspect, the invention relates to a device forcontinuously synthesizing ferrate, comprising a holding chamber; a movercontrollably connected to the holding chamber such that at least aportion of a content of the holding chamber is transferred to the mover;a heating chamber, through which at least a portion of the mover moves;an output opening in the heating chamber through which the content onthe mover is adapted to be transported to a site of use, where the siteof use is proximal to the heating chamber.

[0144] In certain embodiments, the mover comprises a conveyor belt. Thebelt is made of materials that can withstand temperatures higher thanroom temperature. These materials may include, but not be limited to,rubber, steel, aluminum, glass, porcelain, etc.

[0145] Some of the embodiments of the invention relate to a device thatfurther comprises a mixer between the holding chamber and the mover.

[0146] In other embodiments, the heating chamber further comprises atemperature control device.

[0147] Other embodiments of the invention relate to a device thatfurther comprises a storage chamber after the output opening in theheating chamber. Therefore, the conveyor belt may deposit the heatedmixture into this storage chamber following the heating event.

[0148] One embodiment of the device of the present invention is depictedin FIG. 2. Starting materials are added to holding chambers 201. Someembodiments of the invention exhibit only one holding chamber 201, whileothers exhibit two or more holding chambers 201. The starting materialsare then combined and added to a belt 203 that carries the startingmaterials through a heating chamber 205. The starting materials may becombined prior to their placement on the belt 203, or may be mixed onthe belt 203 after they have been placed there separately.

[0149] The embodiment depicted in FIG. 2 shows that the holding chambersempty their contents into a single pipe which in turn empties thestarting material through opening 211 onto the belt 203. However, inother embodiments, each holding chamber may separately empty itscontents onto the belt 203.

[0150] In some embodiments, the flow of material between the holdingchambers 201 and the belt 203 may be controlled. The flow is controlledeither by the presence of a pump or a valve (207) after each holdingchamber 201, or by the presence of a pump or a valve (209) before theopening 211, or by a combination thereof. In certain embodiments, nopump or valve exists between the holding chamber 201 and the opening211.

[0151] In certain embodiments, the starting materials are added directlyonto the belt 203. However, in other embodiments, the starting materialsare added into containers that are placed on the belt. Startingmaterials may be added into the containers before positioning thecontainers on the belt, or the containers may be positioned on the beltbefore the starting materials are added.

[0152] The heating chamber 205 comprises a heating unit that can heatthe temperature within to above room temperature. Various heating unitsare known in the art. In FIG. 2, the heating chamber 205 is depicted asa cylinder, though those of skill in the art realize that the heatingchamber may have any shape, such as a cube or a sphere or the like. Theheating unit 205 may also exhibit a temperature control unit.

[0153] The speed with which the belt travels through the heating unit,the length of the heating unit, and the temperature of the heating unitcan be controlled by the operator in order to ensure that the necessaryyield of ferrate is achieved. Therefore, the device of the presentinvention may exhibit a quality control device at the exit end of theheating unit (213) that can determine the yield of ferrate in themixture. The quality control device may be a chemical sensor, aphotochemical sensor, a spectrophotometer, or the like. The qualitycontrol device may be connected to a computer that can control the speedof the belt through the heating unit and/or the temperature of theheating unit. Therefore, if the yield of ferrate is too low, the devicemay automatically decrease the speed of the belt and/or increase thetemperature of the heating unit. Similarly, if the yield of ferrate istoo high, the device may automatically increase the speed of the beltand/or decrease the temperature of the heating unit. In otherembodiments, the quality control device issues a signal to the operatorof the device, where the operator may manually adjust the speed of thebelt and/or the temperature of the heating unit.

[0154] At the exit end of the heating unit 213, ferrate is removed fromthe belt 203 and is delivered to the site of use. In some embodiments,ferrate just falls off the belt 203 and into a receiving chamber 217,where it can be delivered to the site of use through the opening 215. Inother embodiments, where ferrate is in a container, the container isremoved from the belt and the contents thereof are emptied into thereceiving chamber, either manually or automatically.

[0155] After removing the ferrate from the belt 203, the belt 203 thenloops around to receive more ferrate and repeat the process.

[0156] C. Electrochemical Production Device

[0157] In another aspect, the invention relates to a device forcontinuously synthesizing ferrate, comprising a reaction chambercomprising at least two electrodes and a solution of an iron salt, wherethe electrodes provide sufficient electric current to convert thesolution of an iron salt to a solution of ferrate; a holding chambercontrollably connected to the reaction chamber, into which the solutionof ferrate is kept for a period of time; and an output opening in theholding chamber through which the mixture is adapted to be transportedto a site of use, where the site of use is proximal to the holdingchamber.

[0158] In some embodiments the reaction chamber further comprises amechanical agitator.

[0159] In other embodiments the reaction chamber comprises a tubeconfigured to mix the mixture as it passes through the tube.

[0160] In certain other embodiments the reaction chamber furthercomprises a temperature control device.

[0161] Some other embodiments of the invention further comprise a pumpdownstream from the reaction chamber and upstream from the holdingchamber. This pump controls the flow of material out of the reactionchamber and into the holding chamber.

[0162] In some of the embodiments of the invention the holding chambercomprises a tube located between the reaction chamber and the outputopening.

[0163] One embodiment of the device of the present invention is depictedin FIG. 3. The figure depicts a holding chamber 301. Other embodimentsof the invention may exhibit additional holding chambers, depending onthe number of ingredients added initially. Some embodiments of theinvention may exhibit two or more holding chambers 301. The holdingchamber is connected to the reaction chamber 303. In some embodiments,the flow of material between the holding chamber 301 and the reactionchamber 303 may be controlled by the presence of a pump or a valve (307)after the holding chamber 301. If there are more than one holdingchambers 301, then the flow may be controlled either by the presence ofa pump or a valve (307) after each holding chamber 301, or by thepresence of a pump or a valve before the reaction chamber 303, or by acombination thereof. In certain embodiments, no pump or valve existsbetween the holding chamber 301 and the reaction chamber 303.

[0164] The reaction chamber 303 comprises at least two electrodes 321.The electrodes are connected via wires 319 to a power source 317. Thepower source 317 may be an AC or a DC power source. The electrodes 321and the power generated by the power source 317 are such that they areable to electrochemically oxidize iron, in any oxidation state below +4,to ferrate. In some embodiments, one of the electrodes is an ironelectrode, which serves as both an electrode and as the source of ironfor the production of ferrate. If the electrode is an iron electrode,there may or may not be a need for having a holding chamber 301 in thedevice. An “iron electrode” includes any electrically conductingmaterial comprising iron.

[0165] The reaction chamber 303 is connected with an output opening 315,through which the product of the reaction is transferred to the site ofuse. The flow from the reaction chamber 303 to the output opening 315may be controlled. The control may be through the use of a pump or avalve (313). In certain embodiments, no pump or valve exists between thereaction chamber 303 and the output opening 315.

[0166] In certain embodiments, there is a second holding chamber 305between the reaction chamber 303 and the output opening 315. The secondholding chamber may serve as a storage place for the generated ferratebetween the time of its generation and the time of its use. The flowbetween the reaction chamber 303 and the second holding chamber 305 maybe controlled through the use of a pump or a valve (311).

[0167] In some embodiments, the device of the present invention alsofeatures a temperature control unit. The temperature control unitcontrols the temperature of the holding chambers 301, the reactionchamber 303, the second holding chamber 305, or a combination thereof,or the temperature of the entire device. These components may be held atroom temperature, at a temperature above room temperature, or at atemperature below room temperature, depending on the reaction conditionsand the needs of the particular use contemplated.

[0168] IV. Purification/Separation of Ferrate

[0169] The ferrate produced by the methods of the present invention maybe used without substantial purification. By “substantial purification”it is meant a purification step that brings the purity of the ferrate inthe solution to greater than 99%, that is, a substantially pure ferratesolution is a solution in which more than 99% of the solutes compriseferrate and its counter-ion.

[0170] However, the ferrate solution generated by the methods of thepresent invention may be somewhat purified or undergo a separation step.For example, the ferrate solution may be filtered to remove undissolvedsolids. The filtration may be physical filtration, in which particlesthat are too big to pass through the filter pores are removed, orsurface filtration, where the particles are captured on the surface offilter grains, or a combination of one or more filtration processes.

[0171] Ferrate may also be purified using ion exchange purification. Inthis process, ferrate ions are reversibly bound to a solid statematerial, the column is purged of unwanted impurities, and then theferrate is released from the column. The solid state material of the ionexchange column may be any of the solid state materials currently used,or designed later, for this purpose, and include without limitation,clays, zeolites, phosphonates, titanates, heteropolyacid salts, layereddouble hydroxides, inorganic resins, organic resins, and gel-typeexchangers (e.g., as small beads in several mesh sizes), andcarbon-based inorganic exchangers. Additionally, inorganics can beincorporated into organic resins to make composite exchangers forpurifying ferrate.

[0172] Membranes used for purification of ferrate may be made ofmaterials such as organic polymeric materials. The membrane materialscan be cellulose or polyamide (for example, fully aromatic polyamide TFCmembranes). Other membranes include, but are not limited to,microfiltration, ultrafiltration, and inorganic nanofiltrationmembranes. These membranes are generally made from glass, ceramics, orcarbon.

[0173] Ferrate may also be purified in a direct electric fieldtechnique, during which a direct current electric field is appliedacross a pair of electrodes. The ferrate ions in the liquid phase aremoved under the action of the field to a desired location where they arepumped out for use. The ferrate transport under the action of anelectric field can be electromigration, electroosmosis, orelectrophoresis.

[0174] The ferrate solution produced by the methods of the presentinvention may also be stored in a sedimentation tank for a period oftime and the supernatant then decanted or pumped out. The ferratesolution may also pass through a centrifuge where the solution is spunsuch that the heavier particles in the solution sink to the bottom andthe supernatant, comprising purified ferrate, is removed for furtheruse.

[0175] In certain other embodiments, the ferrate produced by the methodsof the present invention is encapsulated in a membrane for future use.The membrane may be molecular sieves, clay, porcelain, or other porousmaterial that are not susceptible to oxidation by ferrate. Then, to usethe ferrate, at least a portion of the membrane is contacted with theaqueous or gaseous mixture to be treated.

[0176] The membrane may also be slightly water soluble so that asportions of it are dissolved away, more ferrate is exposed to theaqueous mixture to be treated. In this embodiment, the use of ferratemay be in a time-release manner, the time of the release being definedby the solubility of the layers of the membrane.

[0177] The devices disclosed herein may also feature a purificationcomponent that purifies ferrate consistent with the purification methodsdescribed herein.

[0178] V. Uses of Ferrate

[0179] In another aspect, the invention relates to a method of treating,at a site of use, an aqueous mixture having one or more impurity,comprising continuously generating ferrate in a reaction chamber locatedproximal to the site of use; contacting the ferrate with the aqueousmixture at the site of use, whereby at least a portion of the impurityis oxidized.

[0180] In certain embodiments, the impurity is selected from the groupconsisting of a biological impurity, an organic impurity, an inorganicimpurity, a sulfur-containing impurity, a nitrogen-containing impurity,a metallic impurity, and a radioactive impurity, or a combinationthereof. Other impurities are as described herein.

[0181] An “impurity” is defined to be any component of a solution or asystem, whose presence within that solution or system is repugnant tothe contemplated use of that solution or system. Biological impuritiesare those that have a biological origin. Thus, any cells, bacteria,viruses, tissues, etc., or components thereof, whether from plants oranimals, are considered to be biological impurities. Organic impuritiesare chemical compounds that contain at least one carbon atom. Inorganicimpurities are chemical compounds that contain no carbon atoms. Asulfur-containing impurity is one which contains at least one sulfuratom. A nitrogen-containing impurity is one which contains at least onenitrogen atom. A metallic impurity is one which contains at least onemetal atom, whether main group metal, transition metal, or f-blockmetal. A radioactive impurity is one which undergoes radioactive decay,whether by emitting α, β, or γ particles. Those of skill in the artrecognize that a particular impurity may fall within more than onecategory listed above. For example, calcium ethylenediaminetetra-acetate (EDTA) impurity in water is an organic impurity, anitrogen-containing impurity, and a metal-containing impurity.

[0182] The ferrate for use in the treatment method is produced by one ofthe methods set forth herein, i.e., the chemical production, the solidstate production, or the electrochemical production.

[0183] The ferrate produced by the above methods is contacted with theaqueous mixture to be treated. In some embodiments the contacting stepcomprises adding the ferrate to a stream of the aqueous mixture. Inother embodiments, the contacting step comprises contacting the ferrateto a pool of the aqueous mixture. In yet other embodiments thecontacting step comprises contacting a stream of the aqueous mixturewith a stationary container containing the ferrate.

[0184] Generally, the ferrate produced by the process of this inventioncan be used in connection with any known process and for any knownpurpose. The ferrate produced by the process of this invention isespecially useful as an oxidant, flocculent and/or coagulant. Inparticular, potential uses of ferrate produced by the process of thisinvention include the following: removal of color from industrialelectrolytic baths; manufacture of catalysts for the Fischer-Tropschprocess to produce reduced hydrocarbons from carbon monoxide andhydrogen; purification of hemicellulose; selective oxidation of alkenes,alkyl side chains, organic sulfur compounds, thiols, sulfinic acids,organic nitrogen compounds, carboxylic acids, halides, alcohols andaldehydes and in oxidative coupling; as a general oxidant for water,waste water and sewage treatment; disinfection as a biocide or virocide;phosphorylase inactivator; anti-corrosion paint additive; denitration offlue gas; electrodes for batteries; detoxification of cyamide andthiocyanate from waste waters; oxygen demands measurement; cigarettefilters to remove HNC and carcinogenic molecules; oxidizer for hazardouswastes and other waste solutions such as from the pulp industries;pollution control in the removal of hydrogen sulfide from low pressuregas streams; removal of pollutants with mutagenic and carcinogeniccharacters such as naphthalene, nitrobenzene, dichlorobenzene andtrichloroethylene from waste water and drinking water withoutcoproduction of harmful products; additive to cements as structuralhardener; disinfectant to inactivate E. coli, Salmonella, Shigella, andother fecal coliform as a bacterial cell removal step; removingStreptococcus and Staphylococcus; biofouling control with non-corrosiveoxidant for removal of slime films formed of microorganisms such as inelectric power plants and shipboard cooling systems; removal ofbacteria, heavy metals and inorganics in drinking water in an oxidationcoagulation processes; removal of hydrogen sulfide from sour gas in the“Knox” process; delignification of agricultural residues to produceglucose and ethanol from wheat straw; magnetic filler of barium andstrontium ferrate for flexible plastics having high polymer bindercontents; support for other oxidizers such as chromium (VI) and KMnO₄;denitrification of sinter furnace off-gas; removal of impurities fromsolutions fed to zinc plants; decontamination of waste waters containingcyamide and thiocyanate; oxidative destruction of phenol, sulfite andthiosulfate; as a catalyst in burning of coal to remove impurities insteam gasification step; component of grinding wheels; etching agent influid form for evaporated films; and ceramic encapsulated rare earthmetal ferrates for use in electronics where ferromagnetic properties areneeded. These and other applications are discussed in Deininger, U.S.Pat. Nos. 5,202,108, 5,217,584, and 5,370,857, all of which areincorporated herein by reference in their entirety.

[0185] Additional uses of ferrate are discussed below.

[0186] A. Waste Water Treatment

[0187] As noted above, there is a need for development of safe,inexpensive and “environmentally friendly” oxidants, especially forwater and wastewater treatment applications. The treatment of industrialand municipal effluents containing hazardous organic and inorganiccompounds is an important research endeavor. Currently, several methodsfor contaminant removal exist, including adsorption, coagulation,biodegradation, chemical degradation, and photodegradation. Chemicaldegradation is often the most economically feasible as well as theeasiest method for water treatment and usually involves chlorine,hypochlorite, or ozone. Although effective, these oxidants often havedeleterious side effects. Chlorine and ozone are poisonous and highlycorrosive gases.

[0188] Hypochlorite is generally supplied as a solid or in aqueoussolution; however, it is generated using chlorine gas and can rapidlydecompose back into chlorine upon heating or chemical mishandling. Also,although hypochlorite, OCl⁻, is used as a chlorine source for watertreatment at smaller operations, it is expensive.

[0189] Additionally, the handling of chlorine, or hypochlorite, posespotential danger to workers due to its high toxicity. A majordisadvantage of chlorine and chlorine-containing oxidants is that excesschlorine can produce chlorinated oxidation products (e.g., chloramines,chlorinated aromatics, chlorinated amines or hydrocarbons), many ofwhich are potential mutagens or carcinogens, and may be more toxic thanthe parent contaminants and/or more difficult to remove. Because thesecompounds potentially constitute a health hazard for the public, a moveaway from chlorine use is needed.

[0190] The ferrate produced by the methods of the present invention maybe used in treating waste water, sewage, or sludge. It is well known inthe art that ferrate reacts with organic or inorganic compounds andbiological entities, such as cells, bacteria, viruses, etc. In thisreaction, the substrates are oxidized to biologically inactive products.The ferrate molecule itself is reduced to Fe(III), which precipitatesout of the solution as Fe(OH)₃ or other Fe(III) salts. The ironcontaining salts can be easily filtered out, leaving iron-free watercontaining innocuous by-products.

[0191]Escherichia coli, Salmonella, and Shigella are all members of theEnterobacteriaceae. These bacteria and certain others known to those ofskill in the art have similar physiological characteristics, includingbeing rod shaped gram-negative facultatively anaerobic organisms. E.coli has long been used as an indicator of fecal pollution in watersystems and there is a large volume of disinfection literature availablefor this particular organism. Ferrate is an effective biocidal agentagainst suspended bacterial cultures in clean systems. Ferrate has thecapacity to rapidly inactivate several known pathogens at fairly lowconcentrations.

[0192] Ferrate is also an effective disinfectant against viruses, suchas the F2 virus. Ferrate has been studied for its antiviral activitiesand has been found to be effective in inactivating viruses (Kazama, Wat.Sci. Tech. 31(5-6), 165-168 (1995).) Ferrate also coagulates turbidityin water system and inactivates most enteric pathogens at ferrateconcentrations which are reasonable for use in a water and wastewatertreatment facility.

[0193] The biocidal properties of ferrate have also been investigated(Y. Yamamoto, Mizu Shori Gijutsu, Vol. 24, p, 929 (1983)). An importantproperty of ferrate toward its application as a water treatment agent isits ability to act as a potent biocide. Ferrate has been used fordisinfection in river water treatment, as well as in municipal sewagetreatment processes; with its use, removal of coliform bacteria dependson the pH. It has been shown to be effective against E. coli andsphaerotilus (F. Kazama, J. Ferment. Bioeng., Vol. 67, p.369 (1989)).Ferrate has also been used to remove coliform bacteria from treatedsewage and river water (F. Kazama and K. Kato, Hamanashi DaigakuKogakubu Kenkyu Hokoku, Vol. 35, p.1 17 (1984)).

[0194] In addition, ferrate can be used to oxidize ammonia in thesecondary effluent from water treatment plants. The major oxidationproduct is nitrogen, while some nitrites are also present in theproducts. Both of these oxidation products are environmentally friendly.

[0195] The above properties of ferrate can be exploited at municipal orindustrial water treatment plants. A ferrate producing device can beinstalled in close proximity of the water treatment facility. Waste fromthe municipal sewer lines or the industrial effluent lines is mixed withfreshly produced ferrate on site. The ferrate producing device canproduce as much or as little ferrate as is necessary to react with allthe waste present in the effluent.

[0196] Since ferrate is an efficient disinfectant, it has potential foruse in lieu of extensive chlorination of drinking water. As pollutionincreases, the need exists for a water purifying agent that can besafely used by the individual on “small” quantities of drinking water aswell as at the municipal/industrial wastewater level. Such purificationagents should ideally be able to disinfect and remove suspendedparticulate materials, heavy metals (including radioisotopes) and someorganics through flocculation, in order to at least partially destroydissolved organic contaminants through oxidation, and as a final step,to remove itself from solution. A one-step purification reagent whichmeets these criteria is FeO₄ 2-, ferrate. This ion is able tosuccessfully compete with the current two-step, chlorination/ferricsulfate, flocculation technique, thereby circumventing the production oftoxic or carcinogenic halogenated organics.

[0197] Since ferrate has multipurpose oxidant-coagulant properties, itis very attractive for the treatment of waste produced by chemical andpharmaceutical companies. These companies spend billions of dollars ayear in clean up costs for contaminated water used, or produced, intheir processes. Almost all of the waste produced by these companies canbe oxidized to relatively harmless by-products by ferrate, leaving waterthat can be released to the municipal sewage systems and be treatedwithout any special care. Thus, any company that produces waste waterlaced with organic, inorganic, or biological impurities can install aferrate producing device at the end of its effluent line.

[0198] Municipal sewage systems suffer a special burden. They areoverloaded with any imaginable waste, most of which is organic orbiological. Once the large objects are filtered out, the sewerfacilities must deal with the soluble waste remaining behind. Normally,waste water facilities filter the waste water through activated charcoalor other filters that have an affinity for organic compounds, orbiologically treat the wastewater. These processes are slow and costly.The slow response of these facilities to the in-flow of wastewater oftenresults in sewer overflows during storms. In coastal communities thisresults in raw and untreated sewage spilling into the ocean or lakenearby, causing environmental damage. While oxidants may easily be usedto remove the unwanted waste rapidly, the oxidants currently availableon the market are either cost prohibitive, or produce by-products thatare at times more environmentally unsafe than the waste itself.

[0199] Also, there is a vital need for new methods for H₂S control inmunicipal sanitary sewer systems and treatment plants, and industrialwaste treatment facilities. One of the ongoing major problems in wastewater treatment is severe corrosion of facility structures from contactwith hydrogen sulfide gas, H₂S, or its oxidation products after contactwith air. Equally important are the health risks from exposure to H₂Sgas for even short periods of time; such exposure is reported to be theleading cause of death among sanitary sewer workers. Another majorproblem with the evolution of H₂S gas is its foul smell that causesdiscomfort to those exposed to it.

[0200] Ferrate is known to be useful in a variety of waste watertreatment applications. Ferrate oxidations, and their application towaste water treatment, have been studied with a view toward usingferrates in several industrial applications, in particular with a numberof organic and inorganic substrates. (J. D. Carr, P. B. Kelter, A.Tabatabai, D. Spichal, J. Erickson, and C. W. McLaughlin, Proceedings ofthe Conference on Water Chlorination and Chemical Environmental ImpactHealth Effects, pp. 1285-88 (1985)). The applicability of ferrate inwaste treatment involves not only its oxidative abilities, but alsoother multipurpose properties, such as its floc formation, disinfectiveproperties, and generally remediative faculties.

[0201] Direct filtration of ground water using ferrate has been examinedat the pilot plant level (T. Waite, Environ. Sci. Technol., Vol. 17,p.123 (1983)). Biofouling control has been investigated (R. L. Bartzattand D. Nagel, Arch. Env. Health, 1991, Vol. 46(5), pp. 313-14 (1991)).The coagulative properties of ferrate have been found to be useful forturbidity removal (S. J. de Luca, C. N. Idle, A. C. Chao, Wat. Sci.Tech. 33(3), 119-130 (1996)). Studies have shown that when modelcondensers were dosed with 10⁻⁵ M solutions of ferrate twice a day, for5 minutes, biofilm growth was inhibited (T. Waite, M. Gilbert, and C.Hare, Water Tech/Qual., pp. 495-497 (1976)).

[0202] Ferrate oxidative destruction of nitrosamines, which are potentcarcinogens, in waste water has been reported (D. Williams and J. Riley,Inorg. Chim. Acta, Vol. 8, p. 177 (1974)).

[0203] Relatively low ferrate doses have been found to profoundly reducethe BOD (biological oxygen demand) and TOC (total organic carbon) indomestic secondary effluents (F. Kazama and K. Kato, Kogabkubu KenkyuKokou, Vol. 35, pp. 117-22 (1984)).

[0204] Ferrate can be employed for the treatment of mill effluent andsewage sludge from municipal sources. Treatment at 125-1000 mg ofK₂FeO₄/L dose levels was found to significantly decrease the chemicaloxygen demand on manganese (CODMn), due to partial oxidation of the highmolecular weight organics. Decreases in the UV spectrum after treatmentwith ferrate have been interpreted as removal of fulvic and humic acidswithin the iron(III) coagulate produced when the ferrate was reduced (F.Kazama and K. Kato, Kogabkubu Kenkyu Kokou, Vol. 34, pp. 100-4 (1984)).

[0205] Polyaminocarboxylates such as diethylenetriaminepentaacetate(DTPA), ethylenediaminetetracetate (EDTA), and nitriloacetate (NTA) aresynthetic ligands that form stable complexes with most of the metals andare used in a variety of industrial applications such as photographicdeveloping, paper production, and textile dyeing.Ethylenediaminedisuccinic acid (EDDS) forms hexadentate chelates withtransition metals and is used in consumer products, e.g., washingpowder. EDTA is a constituent of formulations for chemicaldecontamination of the primary heat transport system of nuclear powerreactors. The presence of heavy metals, along with polyaminocarboxylateshas been reported at many US Department of Energy (DOE) sites. Thesepolyaminocarboxylates are either poorly biodegradable (e.g., EDTA),associated with other safety regulatory issues (e.g., NTA) or littleeffective (e.g., citrate). Ferrate can be applied to degradepolyaminocarboxylates and metal-polyaminocarboxylates to simpleproducts.

[0206] Certain compounds are listed in the EPA Contaminant CandidateList (CCL). These include diazion, disulfoton, fonofos, terbufos,cyanazine, prometon, 1,2-diphenylhydrazine, nitrobenzene, acetochlor,2,4,6-trichlorophenol, and 2,4-dichlorophenol. These compounds can beoxidized by ferrate.

[0207] The gasoline additive methyl tert-butyl ether (MTBE) is aubiquitous groundwater contaminant. The U.S. geological Survey NationalWater Quality Assessment Program has identified it in 27% of urban wellstested. A more recent survey indicated that between 5 and 10% of allcommunity drinking wells in the United States have detectable MTBEcontamination. It persists in petroleum-contaminated aquifers. MTBE ingroundwater can be oxidized to relatively non-hazardous compounds usingferrate.

[0208] Trichloroethene (TCE), a nonflammable solvent used in largequantities in industry, is one of the most common organic ground watercontaminants and is classified as a “probable human carcinogen.” TCE issequentially reduced to dichloroethene (DCE) isomers, chloroethene (CE),and ethene. The use of ferrate in remediating contaminated groundwateris attractive due to ease of field implementation and the relatively lowcost.

[0209] Highly chlorinated phenol derivatives, such as pentachlorophenol(PCP) have been listed as a priority pollutant by the United StatesEnvironmental Protection Agency. PCP is mainly used as a woodpreservative and general biocide. PCP is a suspected carcinogen and itspyrolysis and combustion reaction products are considerably more toxicthan PCP itself. Ferrate can be utilized in degradation of PCP.

[0210] Ferrate can also be applied to effluent streams from agrochemicalindustry. One of the common products from an agricultural industry, theherbicide trifluaraline is a pre-emergent, cellular and nuclear divisioninhibitor. It is highly toxic for humans. Ferrate can be applied toeffluent streams of agrochemical industry containing compounds such astrifluraline.

[0211] Dyes present in wastewater, which originated from the textileindustry, are of particular environmental concern since they giveundesirable color to the waters. They are also generally harmfulcompounds and can lead to toxic byproducts through hydrolysis, partialoxidation, or other chemical reactions taking place in the waste phase.The decolorization and degradation of different classes of textile dyesfrom the textile industry can be achieved using ferrate.

[0212] In pharmaceutical and fine chemical manufacturing, organictransformations are routinely carried out using oxidizing agents basedon transition metal compounds. One of the biggest problem areas insynthetic methodology is selective oxidations. For example, theoxidation of alcohols carried out with Cr(VI) or Mn(VII) lackspecificity and selectivity. Ferrate is selective and specific in thesereactions. The nontoxic properties of the Fe(III) byproduct makesferrate an environmentally safe oxidant. Ferrate can be utilized inorganic synthesis, thereby reducing the environmental impact of theoxidation processes and also reducing their cost (“green chemistry”).

[0213] Thiourea and its derivatives are known corrosion inhibitors andare used as chemical complexing agents to clean scales developed inindustrial equipment, like boilers and nuclear reactors. Because of thetoxicity of thiourea to aquatic organisms, the treatment of boilerchemical cleaning wastes (BCCWs) is required before their disposal.Ferrate can easily remove thiourea and its derivatives from BCCWs.

[0214] Oil refineries and coke processing plants generate sulfur andcyamide containing compounds. These contaminants are toxic andenvironmentally significant due to their offensive odor. In addition,their presence may not be acceptable in the environment due to theirhigh oxygen demand. Ferrate can be applied to petroleum industryeffluents to eliminate odor related to sulfur and cyamide containingcompounds.

[0215] Drinking water supplies are sometimes plagued by odors resultingfrom the presence of manganese(II). Manganese(II) causes aestheticproblems such as colored water, turbidity, staining, and foul taste.Manganese(II) can also accelerate biological growth which furtherexacerbates odor problems. Mn(II) is removed by oxidation of solubleMn(II) with a ferrate to sparingly soluble hydroxide and oxide solidphases, MnOOH(s) and MnO₂(s), respectively.

[0216] Decontamination of chemical warfare agents is required on thebattlefield as well as in pilot plants, and chemical agents production,storage, and destruction sites. Ferrate can oxidize chemical warfareagents such as VX[O-ethyl-S-(2-diisopropylamino)ethylmethylphosphono-thioate], GD(pinacolyl methylphosphonofluoridate), GB(2-propylmethylphosphonofluridate), mustard gas (2,2′-dichlorodiethylsulfide), and HD [bis(2-chloroethyl) sulfide]. Ferrate has manyapplications such as environmentally friendly “hasty” decontamination onthe battlefield where speed and ease of application of the decontaminantis essential.

[0217] During recovery of natural gas and crude oil from offshore andonshore production operations, produced waters are generated, containingcomplexed mixtures of organic and inorganic materials. Approximately, 12billion barrels of produced water are produced in the US annually. Thislarge volume causes major environmental problems. The water toxicity andorganic loading generally characterize the impact of produced water tothe environment. The treatment with ferrate can reduce the organicloading and acute toxicity of the oil field produced water.

[0218] Water supplies containing arsenic compounds are a worldwidehealth concern. Tens of thousands of people already show symptoms ofarsenic poisoning. A maximum of ten microgram/L of arsenic in water isthe threshold value recommended by the World Health Organization and theEuropean Community. Current removal procedures are not adequate to meetcriteria for ambient arsenic in water supplies. Steps involvingoxidation, adsorption, and precipitation can be carried out by ferratein removing arsenic from water.

[0219] In recent years, there has been increasing concern for thepresence of natural organic matter (NOM) in potable surface and groundwater supplies. One reason for concern is related to the formation ofdisinfection byproducts (DPB's) from the treatment of water bychlorination methods. Oxidation of NOM by chlorination produceschlorinated hydrocarbons, many of which are known or suspectedcarcinogens. Ferrate has excellent potential to serve as anenvironmentally friendly remediation treatment for reducing levels ofDPB's in drinking water. This process would not form toxic chlorinatedorganics and may also effectively mineralize NOM to carbon dioxide,potentially eliminating the production of DPB's entirely.

[0220] Ferrate solution can be used to develop a method for protectingiron and steel castings from corrosion. This procedure is based on theformation of ferric oxide from the decay of the thin film of ferrate onthe metal. In this procedure, a mixture of alkaline metal ferrate andalkaline solution containing a reducing agent is brought into contactwith metal surfaces.

[0221] There are several disadvantages of using metal salts such asalum, ferric chloride, and ferrous sulfate in removing solids from asolution. First, binding of water to the metal ions creates a gelatinoussludge with a high water content that increases dewatering costs.Second, the water becomes more acidic after the addition of salts,causing a decrease in the coagulant property of the salt. Thirdly, theformation of metal-phosphate complexes causes phosphate levels in thesolution to decrease and, as a result, phosphate becomes less availableto bacteria. This upsets the biological function of the system.Synthetic organic polymers are used as common coagulants and flocculentsto replace metal salts. To achieve this end, a large quantity of polymeris required, which makes the process expensive. There are also severaldisadvantages to using a synthetic polymer. Synthetic polymers releasetoxic materials into water due to solubility of polymers. In addition,solubility is also greatly influenced by environmental factors such astemperature and pH. Polymers are very sensitive to the quality of waterand also have little effect on BOD. A combination of polymers andferrate can be advantageous. This combination can require less amount ofcoagulant and thus be cost-effective. Polymer-ferrate complexes can beformed to eliminate the toxicity from the solubility of polymers.Polymer-ferrate complexes can also have multi-purpose properties and canbe less sensitive towards quality of water.

[0222] A ferrate producing device located at a waste water facility willbe useful in overcoming all of the above-described problems faced bythese facilities. The device of the present invention can produceinexpensive ferrate rapidly. Ferrate can be injected into the flow ofwaste water and mixed therewith, thereby oxidizing and removing theunwanted waste. Ferrate oxidation of organic and inorganic compoundsresults in environmentally safe by-products. In addition, the ironcontaining salt by-products can easily be filtered off and removed fromthe waste water. This eliminates the need to repeatedly pass waste waterthrough filters, activated charcoal, or geological reactors, orincubating the waste water in pools of anaerobic bacteria for digestionof the organic waste.

[0223] The on-site generation of ferrate removes two of the problemsassociated with its use today: cost and instability. Because ferrate isproduced on site and can be applied immediately after its production,little or no attention must be paid to the fact that it is unstable. Theferrate is simply introduced into the waste water before it has had achance to decompose. In addition, the application of ferrate requires noneed for purification, crystallization, or storage; therefore, the costof its use is very low. Furthermore, the ferrate produced by the deviceof the invention requires lesser amounts of expensive feed stock.

[0224] B. Treatment of Recreational Water

[0225] The ferrate generated by the methods of the present invention canbe used in pool and spa applications. It is well known that pools,Jacuzzis, and spas become polluted with organic waste. The waste entersthe water from the body of the swimmers or by wind or insects. If leftuntreated, the water becomes turbid and foul. Usual methods of treatmentinclude the addition of oxidants such as bleach and anti-bacterial oranti-fungal agents. These treatments create unwanted side-effects. Theoxidants that are left in the water have an adverse effect on the skinof the swimmers using the water. In addition, the oxidants createenvironmentally harmful by-products, such as chlorinated hydrocarbons.

[0226] The device of the present invention can be fitted to any swimmingpool or Jacuzzi such that the ferrate produced by the device is mixedwith the water in a mixing chamber, whereby all the organic waste isoxidized to innocuous products, the iron salts are filtered away, andthe clean water is re-introduced into the pool. This represents a highlyeffective and cost-efficient method of cleaning the pool water, sinceferrate produced by the methods of the present invention is less costlyin the long run than purchasing the numerous oxidants and anti-fungalchemicals necessary to treat a pool.

[0227] C. Use in Processing Plants

[0228] Many processing plants generate aqueous streams comprisingbiosolids such as proteins, carbohydrates, fats, and oils which must betreated to remove the potentially valuable biosolids products before thestream can be discharged from the plant. These aqueous streams are oftenderived from food processing plants and have solids contents of about0.01% to 5% on a weight basis. This invention provides a process forclarification of such streams, whereby the solids are flocculated, andbiosolids are optionally separated from the solids. The biosolids cansubsequently be used, for example, in animal feeds.

[0229] As defined herein, to “flocculate” means to separate suspendedbiosolidsfrom a stream comprising biosolids, where the biosolids becomeaggregated and separate to the top or bottom of the stream in which thebiosolids had previously been suspended. Flocculation produces aflocculated material, which, if desired, can be physically separatedfrom the stream. In the present invention, it is desirable to maximizethe size of the flocculated material in order to facilitate removal ofthis material from the stream.

[0230] The process of this invention involves treating an aqueous streamcomprising biosolids by contacting the stream with ferrate. The aqueousstream can be derived from any number of processes, which generate suchstreams, such as from animal and vegetable processing, includingprocessing for non-food uses.

[0231] In the process of this invention, the aqueous stream to betreated can be from any processing plant that produces an aqueous streamcomprising biosolids, such as food processing plants. For example,animal slaughterhouses and animal processing plants and other foodprocessing plants may produce aqueous streams comprising protein, fatsand oil. Animal slaughterhouses and processing plants include those forcattle, hogs, poultry and seafood. Other food processing plants includeplants for vegetable, grain and dairy food processing plants forprocessing soybeans, rice, barley, cheese, and whey; plants forwet-milling of starches and grains; as well as breweries, distilleriesand wineries. Biosolids present in aqueous streams from these processesmay include sugars, starches and other carbohydrates in addition toprotein, fats, and oils. For example in processing soybeans, proteinsare extracted into an aqueous stream from which they are subsequentlyrecovered. The present invention is especially useful for treatingstreams from animal processing, and more particularly, from poultryprocessing.

[0232] While this invention is useful in conventional food processingoperations, which produce aqueous suspensions of biosolids, it should berecognized that this invention is also useful in treatment of aqueoussuspensions of biosolids derived from processing of food (animal orvegetable) materials, which may have non-food end uses. For example,when separated and recovered, proteins are useful in certain cosmeticsand other skin care formulations; starch has numerous non-food uses,including uses in paper manufacture. Further still, this invention isuseful to treat in general, any aqueous stream comprising biosolids,which may result from non-food processing operations. Moreover, thoughthe biosolids, as disclosed above, are generally suspended in asubstantially aqueous stream, the concentration of biosolids dissolvedin the stream depends on the properties of the stream or the biosolidssuch as, for example, pH, salinity, or other parameters.

[0233] The process of this invention involves treatment of an aqueousstream containing biosolids, for example, proteins, to reduce suspendedsolids (as measured by turbidity) and optionally to separate thebiosolids. The biosolids can be recovered for subsequent use. It shouldbe recognized that this process can capture both suspended biosolids aswell as soluble materials, such as those present in blood and sugars.

[0234] The flocculated biosolids can optionally be separated from thetreated stream by conventional separation processes such assedimentation, floatation, filtering, centrifugation, decantation, orcombinations of such processes. The separated biosolids can subsequentlybe recovered and used in numerous applications. It has also beensurprisingly found that the recovered biosolids from this process havereduced odor when dry relative to those recovered from a process usingferric chloride as part of a flocculating system. The flocculatedbiosolids can be separated and recovered by known techniques, such asthose mentioned above.

[0235] E. Use in Radioactive Clean Up

[0236] The process of the present invention is also useful for theprecipitation of radioactive materials, particularly uranium, dissolvedin aqueous solutions. The dissolved radioactive materials may be from anaturally flowing stream, or a uranium mining operation water treatmentplant. The water from the stream is destined to be treated by aconventional city water treatment facility for drinking and home use.

[0237] Ferrate has been proposed as a treatment agent for the removal ofradionuclides (transuranics) from waste water. To date, the focus hasbeen on the nuclear industry, where ferrate is used to remove uraniumand transuranic elements from contaminated water. In addition, there iscurrently an interest in using ferrate in the removal of plutonium andamericium from waste water effluent.

[0238] U.S. Pat. No. 4,983,306 to Deininger discloses a method fortransuranic element polishing from radioactive wastewater using FeO₄ ²⁻that involves adjusting the pH of a transuranic element-containing watersource to a range of 6.5-14.0. Supposedly, removal occurs byco-precipitation of the transuranics within the ferric hydroxide matrixsimilar to other heavy metals. Also, small amounts of a chemical areused compared to common technology. Based on chemical dosages,radioactive sludge generation using this method is reduced by 3-20%,depending on the suspended solids content in the wastewater feed(Deininger, et al., Waste Manage. '90, vol. 1, pp. 789-795 (1990)).

[0239] F. Use in Surface Cleaning

[0240] Dilute solutions of ferrate can be used for oxidizingpretreatment of chromium (III) oxide containing films, resulting fromcorrosion of base metal surfaces of piping systems and the like, torender the corrosion films more amenable to conventional chemicalcleaning treatments. There is an existing need for replacement ofcurrently used laboratory oxidants, especially the chromate derivatives.Chromate and chlorine are of environmental concern, and in chromateoxidations, Cr(III) is formed, which is a suspected carcinogen. Also, inpermanganate reactions, MnO₂ is generated.

[0241] Removal of heavy metals, such as Cu, Cd, and Mn using ferrate isalso known. Ferrate has been shown to remove colloidal suspensions andheavy metals through flocculation (T. Suzuki, Odaku Kenkyu, Vol. 11 (5),p. 293-296 (1988)). The mechanism for Mn removal involves the oxidativeformation of insoluble MnO₂ and subsequent entrapment of these metalsinto the Fe(OH)₃ precipitate resulting from ferrate's reduction product.Cu and Cd are removed in a similar manner. The removal of heavy metalions and humic acid by coagulation after treatment with potassiumferrate has been studied. Metal ions are generally trapped duringsedimentation (F. Kazama and K. Kato, Kogyo Yosui, Vol. 357, p. 8-13(Chemical Abstract 110:63421y) (1988)).

[0242] Additionally, metallic surfaces, such as those used in medicaldevices or in the semi-conductor industry, need to be cleaned ordisinfected. Current methods for cleaning metal surfaces require theirexposure to disinfectants, such as bleach, that are highly corrosive.Consequently, the metal parts corrode and routinely fail due to fatigueand need to be replaced. Aside from the high cost of replacing thecorroded metal pieces, the failure of the instruments create discomfortand annoyance for the users and liabilities for the manufacturers.

[0243] Ferrate produced by the methods of the present invention can beused to clean the surfaces of these metal parts. Ferrate is notcorrosive and does not damage the integrity of the metal piece. Asmentioned above, the biocidal activity of ferrate is comparable to thatof bleach. Therefore, ferrate provides an efficient, effective, andeconomical means by which these metal surfaces can be cleaned.

[0244] G. Medical Uses

[0245] In the medical arts, there is a great need to disinfect and cleaninstruments and surfaces. The ferrate generating device of the presentinvention can be used in a hospital setting for such a use.

[0246] In certain other embodiments, the ferrate generated by themethods of the present invention may be used to treat a wound, asdescribed in U.S. Pat. No. 6,187,347, which is incorporated herein byreference in its entirety.

[0247] VI. Some Embodiments of the Invention

[0248] Some of the embodiments of the invention refer to the following:

[0249] A method of continuously synthesizing ferrate, comprising:

[0250] a) mixing an aqueous solution comprising an iron salt and anoxidizing agent in a mixing chamber;

[0251] b) delivering at least a portion of the aqueous solution to areaction chamber;

[0252] c) continuously generating ferrate in the reaction chamber;

[0253] d) delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and

[0254] e) adding additional aqueous solution to the mixing chamber.

[0255] The above method, where the additional aqueous solution in step(e) is added in an amount to substantially replace the portion of theaqueous solution delivered to the reaction chamber.

[0256] The above method, further comprising adding a base to the aqueoussolution.

[0257] The above method, where the base comprises an ion selected fromthe group consisting of a nitrogen base, the hydroxide ion, the oxideion, and the carbonate ion, or a combination thereof.

[0258] The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0259] The above method, where the oxidizing agent comprises at leastone of the following: a hypohalite ion, a halite ion, a halate ion, aperhalate ion, ozone, oxone, halogen, a peroxide, a peracid, a salt of aperacid, and Caro's acid, or a combination thereof.

[0260] The above method, where the oxidizing agent comprises ahypohalite ion selected from the group consisting of the hypochloriteion, the hypobromite ion, and the hypoiodite ion.

[0261] The above method, where the oxidizing agent comprises a haliteion selected from the group consisting of the chlorite ion, the bromiteion, and the iodite ion.

[0262] The above method, where the oxidizing agent comprises a halateion selected from the group consisting of the chlorate ion, the bromateion, and the iodate ion.

[0263] The above method, where the oxidizing agent comprises a perhalateion selected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

[0264] The above method, additionally comprising repeating steps (b)through (d).

[0265] A method of treating, at a site of use, an aqueous mixture havingat least one impurity, comprising

[0266] a) continuously generating ferrate in a reaction chamber locatedproximal to the site of use;

[0267] b) contacting the ferrate with the aqueous mixture at the site ofuse,

[0268] whereby at least a portion of the impurity is oxidized.

[0269] The above method, where the impurity is selected from the groupconsisting of a biological impurity, an organic impurity, an inorganicimpurity, a sulfur-containing impurity, a metallic impurity, and aradioactive impurity, or a combination thereof.

[0270] The above method, where the step of continuously generatingferrate comprises the steps of:

[0271] a) mixing an aqueous solution comprising an iron salt and anoxidizing agent in a mixing chamber;

[0272] b) delivering at least a portion of the aqueous solution to areaction chamber;

[0273] c) continuously generating ferrate in the reaction chamber;

[0274] d) delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and

[0275] e) adding additional aqueous solution to the mixing chamber.

[0276] The above method, where the additional aqueous solution added instep (e) is in an amount to substantially replace the portion of theaqueous solution delivered to the reaction chamber.

[0277] The above method, further comprising adding a base to the aqueoussolution.

[0278] The above method, where the base comprises an ion selected fromthe group consisting of the hydroxide ion, the oxide ion, and thecarbonate ion, or a combination thereof.

[0279] The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0280] The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, oxone, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

[0281] The above method, where the oxidizing agent comprises ahypohalite ion selected from the group consisting of the hypochloriteion, the hypobromite ion, and the hypoiodite ion.

[0282] The above method, where the oxidizing agent comprises a haliteion selected from the group consisting of the chlorite ion, the bromiteion, and the iodite ion.

[0283] The above method, where the oxidizing agent comprises a halateion selected from the group consisting of the chlorate ion, the bromateion, and the iodate ion.

[0284] The above method, where the oxidizing agent comprises a perhalateion selected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

[0285] The above method, where the contacting step comprises adding theferrate to a stream of the aqueous mixture.

[0286] The above method, where the contacting step comprises contactingthe ferrate to a pool of the aqueous mixture.

[0287] The above method, where the contacting step comprises contactinga stream of the aqueous mixture with a stationary container containingthe ferrate.

[0288] The above method, additionally comprising repeating steps (b)through

[0289] A device for continuously synthesizing ferrate for delivery to asite of use, comprising:

[0290] a) a first holding chamber;

[0291] b) a second holding chamber;

[0292] c) a mixing chamber controllably connected to the first holdingchamber and to the second holding chamber, into which a content of thefirst holding chamber and a content of a second holding chamber areadded to form a first mixture;

[0293] d) a reaction chamber controllably connected to the mixingchamber, the reaction chamber adapted to receive the first mixture andmaintain the first mixture for a period of time;

[0294] e) a ferrate mixture in the reaction chamber; and

[0295] f) an output opening in the reaction chamber through which theferrate mixture is adapted to be transported to the site of use,

[0296] where the site of use is proximal to the reaction chamber.

[0297] The above device, where the mixing chamber further comprises amechanical agitator.

[0298] The above device, where the mixing chamber comprises a tubeconfigured to mix the mixture as it passes through the tube.

[0299] The above device, where the mixing chamber further comprises atemperature control device.

[0300] The above device, further comprising a pump downstream from thefirst and the second holding chambers and upstream from the mixingchamber.

[0301] The above device, further comprising a pump downstream from themixing chamber and upstream from the reaction chamber.

[0302] The above device, where the reaction chamber comprises a tubelocated between the mixing chamber and the output opening.

[0303] A system for continuously synthesizing ferrate, comprising:

[0304] a) a first holding chamber containing an iron salt;

[0305] b) a second holding chamber containing an oxidizing agent;

[0306] c) a mixing chamber controllably connected to the first holdingchamber and to the second holding chamber, into which the iron salt andthe oxidizing agent are controllably added to form a mixture;

[0307] d) a reaction chamber controllably connected to the mixingchamber, into which the mixture is kept for a period of time, and inwhich ferrate is synthesized, and

[0308] e) an output opening in the reaction chamber through which theferrate is adapted to be transported to a proximal site of use.

[0309] The above system, further comprising adding a base to themixture.

[0310] The above system, where the base comprises an ion selected fromthe group consisting of the hydroxide ion, the oxide ion, and thecarbonate ion, or a combination thereof.

[0311] The above system, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0312] The above system, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, oxone, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

[0313] The above system, where the oxidizing agent comprises ahypohalite ion selected from the group consisting of the hypochloriteion, the hypobromite ion, and the hypoiodite ion.

[0314] The above system, where the oxidizing agent comprises a haliteion selected from the group consisting of the chlorite ion, the bromiteion, and the iodite ion.

[0315] The above system, where the oxidizing agent comprises a halateion selected from the group consisting of the chlorate ion, the bromateion, and the iodate ion.

[0316] The above system, where the oxidizing agent comprises a perhalateion selected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

[0317] The above system, where the mixing chamber further comprises amechanical agitator.

[0318] The above system, where the mixing chamber comprises a tubeconfigured to mix the mixture as it passes through the tube.

[0319] The above system, where the mixing chamber further comprises atemperature control device.

[0320] The above system, further comprising a pump downstream from thefirst and the second holding chambers and upstream from the mixingchamber.

[0321] The above system, further comprising a pump downstream from themixing chamber and upstream from the reaction chamber.

[0322] The above system, where the reaction chamber comprises a tubelocated between the mixing chamber and the output opening.

[0323] A method of purifying drinking water comprising contactingferrate generated by the above methods with the drinking water, wherethe contacting is at a site proximal to the generation site.

[0324] A method of purifying waste water comprising contacting ferrategenerated by the above methods with the waste water, where thecontacting is at a site proximal to the generation site.

[0325] A method of purifying sewage comprising contacting ferrategenerated by the above methods with the sewage, where the contacting isat a site proximal to the generation site.

[0326] A method of cleaning surgical instruments comprising contactingferrate generated by the above methods with the surgical instruments,where the contacting is at a site proximal to the generation site.

[0327] A method of removing radioactive materials from an aqueoussolution comprising contacting ferrate generated by the above methodswith the aqueous solution, where the contacting is at a site proximal tothe generation site.

[0328] A method of cleaning a metallic or a polymer surface comprisingcontacting ferrate generated by the above methods with the metallic or apolymer surface, where the contacting is at a site proximal to thegeneration site.

[0329] A method of coating a metallic or a polymer surface comprisingcontacting ferrate generated by the above methods with the metallic or apolymer surface, where the contacting is at a site proximal to thegeneration site.

[0330] A method of continuously synthesizing ferrate, comprising:

[0331] a) providing a mixture of an iron salt and an oxidizing agent;

[0332] b) continuously delivering at least a portion of the mixture to aheating chamber;

[0333] c) exposing the mixture to elevated temperatures in the heatingchamber, thereby generating ferrate;

[0334] d) removing at least a portion of the ferrate generated in stepc) from the heating chamber;

[0335] e) adding additional mixture to the heating chamber.

[0336] The above method, where the additional mixture added to theheating chamber is in an amount to substantially replace the portion ofthe ferrate removed from the heating chamber.

[0337] The above method, further comprising adding a base to themixture.

[0338] The above method, where the base comprises an ion selected fromthe group consisting of a nitrogen base, the hydroxide ion, the oxideion, and the carbonate ion, or a combination thereof.

[0339] The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0340] The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, halogen, a peroxide, a peracid, a salt of aperacid, and Caro's acid, or a combination thereof.

[0341] The above method, where the oxidizing agent comprises ahypohalite ion selected from the group consisting of the hypochloriteion, the hypobromite ion, and the hypoiodite ion.

[0342] The above method, where the oxidizing agent comprises a haliteion selected from the group consisting of the chlorite ion, the bromiteion, and the iodite ion.

[0343] The above method, where the oxidizing agent comprises a halateion selected from the group consisting of the chlorate ion, the bromateion, and the iodate ion.

[0344] The above method, where the oxidizing agent comprises a perhalateion selected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

[0345] The above method, where the mixture exposed to elevatedtemperature is a solid.

[0346] A device for continuously synthesizing ferrate, comprising:

[0347] a) a holding chamber;

[0348] b) a mover controllably connected to the holding chamber suchthat at least a portion of a content of the holding chamber istransferred to the mover;

[0349] c) a heating chamber, through which at least a portion of themover moves;

[0350] d) an output opening in the heating chamber through which thecontent on the mover is adapted to be transported to a site of use,

[0351] where the site of use is proximal to the heating chamber.

[0352] The above device, where the mover comprises a conveyor belt.

[0353] The above device, further comprising a mixer between the holdingchamber and the mover.

[0354] The above device, where the heating chamber further comprises atemperature control device.

[0355] The above device, further comprising a storage chamber after theoutput opening in the heating chamber.

[0356] A device for continuously synthesizing ferrate, comprising:

[0357] a) a reaction chamber comprising two electrodes and a solution ofan iron salt, where the electrodes provide sufficient electric currentto convert the solution of an iron salt to a solution of ferrate;

[0358] b) a holding chamber controllably connected to the reactionchamber, into which the solution of ferrate is kept for a period oftime; and

[0359] c) an output opening in the holding chamber through which themixture is adapted to be transported to a site of use,

[0360] where the site of use is proximal to the holding chamber.

[0361] The above device, where the reaction chamber further comprises amechanical agitator.

[0362] The above device, where the reaction chamber comprises a tubeconfigured to mix the mixture as it passes through the tube.

[0363] The above device, where the reaction chamber further comprises atemperature control device.

[0364] The above device, further comprising a pump downstream from thefirst and the second holding chambers and upstream from the reactionchamber.

[0365] The above device, further comprising a pump downstream from thereaction chamber and upstream from the holding chamber.

[0366] The above device, where the holding chamber comprises a tubelocated between the reaction chamber and the output opening.

[0367] A method of continuously synthesizing ferrate, comprising:

[0368] a) continuously providing an aqueous solution comprising an ironsalt in a reaction chamber, where the reaction chamber comprises atleast two electrodes;

[0369] b) providing sufficient electric current to the at least twoelectrodes to convert at least a portion of the iron salt to ferrate;

[0370] c) delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and

[0371] d) adding additional aqueous solution to the reaction chamber.

[0372] The above method, where the additional aqueous solution added instep (d) is in an amount sufficient to substantially replace the portionof the aqueous solution delivered to the reaction chamber.

[0373] The above method, further comprising adding a base to the aqueoussolution.

[0374] The above method, further comprising adding an acid to theaqueous solution.

[0375] The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0376] A method of synthesizing ferrate, comprising:

[0377] a) mixing an aqueous solution comprising an iron salt and anoxidizing agent in a mixing chamber to form a solution of ferrate;

[0378] b) delivering at least a portion of the solution of ferrate to asite of use that is proximal to the mixing chamber.

[0379] The above method, further comprising adding a base to the aqueoussolution.

[0380] The above method, where the base comprises an ion selected fromthe group consisting of a nitrogen base, the hydroxide ion, the oxideion, and the carbonate ion, or a combination thereof.

[0381] The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

[0382] The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, oxone, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

[0383] The above method, where the oxidizing agent comprises ahypohalite ion selected from the group consisting of the hypochloriteion, the hypobromite ion, and the hypoiodite ion.

[0384] The above method, where the oxidizing agent comprises a haliteion selected from the group consisting of the chlorite ion, the bromiteion, and the iodite ion.

[0385] The above method, where the oxidizing agent comprises a halateion selected from the group consisting of the chlorate ion, the bromateion, and the iodate ion.

[0386] The above method, where the oxidizing agent comprises a perhalateion selected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

[0387] A method of treating, at a site of use, an aqueous mixture havingat least one impurity, comprising

[0388] a) continuously generating ferrate in a reaction chamber locatedproximal to the site of use;

[0389] b) contacting the ferrate with the aqueous mixture at the site ofuse, whereby at least a portion of the impurity is coagulated.

EXAMPLES Example 1 Preparation of Ferrate(VI)

[0390] The following is one representative embodiment of a laboratoryprocedure for synthesizing ferrate. Add 75 mL distilled water to a 250mL beaker. Add 30 g of NaOH to result in a 10 M solution. Cool thecaustic solution in an ice bath. Pump Cl₂(g) (approximately 6.5 g) intothe solution while mixing. Add a second batch (70 g) of NaOH to thehypochlorite solution. Keep the solution cool. Coarse filter theprecipitated salt residue. Add 25 g of Fe(NO₃)₃.9H₂O while stirring.Filter through medium coarse filter. Analyze the Fe⁶⁺ yield using UV-Visspectroscopy by observing absorbance at about 510 nm.

Example 2 Synthesis and Measurement of Ferrate

[0391] Ferrate is synthesized using the procedure of Example 1, except16.35 g of chlorine was used instead of 6.5 g, and 25 g NaOH is used asthe second caustic addition instead of 70 g. 40 g ofcoarse-glass-frit-filtered caustic/hypochlorite solution is added to a50 mL jacketed reaction vessel containing a TEFLON®-coated magneticstirring bar. Controlled temperature water is circulated through thejacket to control and establish the reaction temperature. 5.0 g offerric nitrate nonahydrate (Fe(NO₃)₃.9H₂O ) is added over a period of afew minutes to begin the experiment. Temperature is set at 30° C.Fraction Actual Actual Expected Observed of Iron Reaction Time, Wt*,Absorb- Absorb- in (VI) Tempera- min (g) ance† ance State ture, ° C.Notes 0 22.4 Begin iron addition 2 27 Complete iron addition 2.5 30 3.533.9 Beginning of reaction noted 5 0.33 1.04 0.25 0.24 31.1 10 0.32 1.010.40 0.40 30.7 17 0.31 0.98 0.48 0.49 30.4 25 0.33 1.04 0.59 0.57 30.435 0.32 1.01 0.60 0.59 30.3 45 0.34 1.08 0.695 0.64 30.5 # in the +6state.

[0392] The concentration of Fe(VI) is measured by the absorbance (A) ofa buffered sample of the reaction product solution, relative to theblank pH 10 buffer solution, with a UV-Vis spectrophotometer set at awavelength of 510 mn. The formula for the${{fraction}\quad {converted}} = \frac{A \times 100 \times {RSW} \times {MWIS}}{{MAC} \times 1000 \times {SW} \times {wt}\quad I\quad \sin \quad R}$

[0393] where

[0394] A=absorbance measurement

[0395] RSW=the reaction solution weight (total weight in grams)

[0396] SW=the sample weight of the reaction solution taken to combinewith 49.7-49.85 g buffer solution (about 0.3-0.15 g, respectively)

[0397] MWIS=molecular weight of the iron source

[0398] wtISinR=weight of iron source used in reaction (in grams)

[0399] 100=volume of buffer solution in cc's

[0400] 1000=volumetric conversion factor for cc/L

[0401] MAC=molar absorptivity coefficient, which is equal to 1150/Mcmfor Fe(VI) in the pH 10 buffer solution at 510 nm

[0402] A=MAC×p×c

[0403] p=path length of the absorbance cell (cm)

[0404] c=concentration of Fe(VI) in g-moles per liter Temperature is setat 35° C. Fraction Actual Actual Expected Observed of Iron ReactionTime, Wt, Absorb- Absorb- in (VI) Tempera- min gm ance ance State ture,° C. Notes 0 24 Begin iron addition 2 28.6 Complete iron addition 2.5 323.5 37 Beginning of reaction noted 5 0.32 0.285 1.01 0.28 36 10 0.340.52 1.08 0.48 35.4 17 0.34 0.61 1.08 0.56 35.3 25 0.34 0.67 1.08 0.6235.3 35 0.31 0.68 0.98 0.69 35.3 45 0.34 0.813 1.08 0.75 35.3 60 0.431.11 1.36 0.82 35.2

[0405] This example shows that, under the given conditions, maximumconversion of Fe(III) and maximum yield of Fe(VI) requires at least 60minutes of reaction time; and that Fe(VI) formation, in this case, isenhanced at 35° C. over that obtained at 30° C.

Example 3 Preparation of Ferrate(VI)

[0406] Ferrate is synthesized using the procedure of Example 1, except13 g of chlorine was used instead of 6.5 g, and 25 g NaOH is used as thesecond caustic addition instead of 70 g. Reaction vessel is a jacketedbeaker maintained at 35° C. Begin with 20 g of caustic/hypochloritesolution. Gradually add 1.6 g of ferric nitrate nonahydrate crystals.This is a 5 fold stoichiometric excess of hypochlorite over ferric(III).The maximum temperature achieved during this step was 39° C. ActualFraction of Actual re- Time, weight, Expected Actual Iron in the actiontemp- min gm absorbance absorbance (VI) state erature, ° C. 15 0.32331.36 0.86 0.63 35.2 30 0.3427 1.44 1.14 0.79 35.2 45 0.2984 1.26 1.100.87 35.2 60 0.3289 1.39 1.25 0.90 35.2

[0407] This example shows that, compared with Example 2, the Fe(VI)yield is increased by using more excess hypochlorite and causticsolution relative to the Fe(III) content of the reaction mixture. Inthis example, the volume of pH 10 buffer solution used was 50 cc insteadof 100 cc. Experiment Fe(NO₃)₃ 9H₂O (g) NaOH (g) Cl₂ (g) A 6.01 13.63.24 B 4.19 13.6 3.47 C 2.41 13.6 3.24

Example 4 Ferrate(VI) Decay Rates

[0408] Ferrate(VI) is synthesized and measured according to theprocedures of Examples 1 and 2, except that the following reactantquantities are used:

[0409] In each case, the jacketed reaction vessel temperature iscontrolled at 35° C. for about the first 2 hours and then allowed toslowly cool to ambient conditions (about 23° C. Experiment A ExperimentB Experiment C Reaction Fraction Reaction Fraction Reaction FractionTime of Fe in Time of Fe in Time of Fe in (min.) (VI) State (min.) (VI)State (min.) (VI) State 0 0 0 0 0 0 15 0.40 15 0.50 28 0.75 30 0.44 300.59 43 0.85 45 0.44 45 0.65 60 0.90 60 0.42 60 0.69 75 0.91 120 0.37 750.71 90 0.93 180 0.34 105 0.73 120 0.93 240 0.29 175 0.74 150 0.93 3000.27 239 0.76 210 0.94 360 0.25 359 0.76 270 0.95 390 0.22 479 0.76 3900.95 1410 0.16 1395 0.58 506 0.96 1500 0.56 566 0.96 1745 0.49 1466 0.922920 0.33 1576 0.91 1816 0.89 2991 0.86

[0410] These experiments show that ferrate(VI) is not stable over longtime periods; however, the stability and the half-life for decompositionimprove with higher ferrate yields. These experiments also exemplify theconcept of generating ferrate at a site proximal to the site of use suchthat the two sites are within a distance that allows for the ferrate totravel the distance within a half-life of its decomposition. In thisexample, the half-life of the ferrate in Experiments A and B isapproximately 400 min and 2250 min, respectively. The half-life offerrate in Experiment C is greater than 3000 min; however, theconsumption of Cl₂ and NaOH per unit weight of Fe(VI) is significantlygreater than that for Experiments A or B.

Example 5 Synthesis of Ferrate(VI) with Commodity Feeds

[0411] In this example, ferrate(VI) is synthesized with readilyavailable commodity liquid bleach (13.4 wt % NaOCl), commodity liquidcaustic (50.5 wt % NaOH), and 50 wt % ferric chloride in water solution.Initially 30.03 g of bleach solution is placed in a beaker containing aTEFLON®-coated magnetic stirring bar and the bleach beaker is cooled inan ice/water bath to about 15° C. Then 37.06 g of caustic solution isslowly added to the bleach with stirring such that the temperature ismaintained at about 15-20° C. The bleach/caustic solution is thentransferred to a jacketed reaction vessel. Then 2.97 g of 50% ferricchloride solution is injected into the bleach/caustic solution with asyringe needle positioned below the liquid level of the stirredbleach/caustic solution. The jacketed reaction vessel controltemperature is then set at 30° C., and sample aliquots (about 0.3 g) aretaken about every 30 minutes for Fe(VI) yield measurements according tothe procedure described in Example 2. In this case, the yield of ferratepeaked out at 68%.

Example 6 Synthesis of Ferrate(VI) with Commodity Feeds

[0412] Ferrate(VI) is synthesized utilizing the same liquid feedmaterials and methodology as those used in Example 5, except 55.59 g ofcaustic solution is used instead of 37.06 g. In this case, the yield offerrate(VI) peaked out at 81%.

Example 7 Preparation of Ferrate(VI)

[0413] Ferrate is synthesized using the procedure of Example 1, exceptthat 17 g of chlorine was used instead of 6.5 g. 40 grams of coarseglass frit filtered solution of hypochlorite in saturated sodiumhydroxide solution is added to a 50 mL Pyrex beaker with a TEFLON®stirring bar. The beaker is placed in a large crystallizing dish on amagnetic stirrer plate. The crystallizing dish has a water/ice mixtureto maintain a temperature of 19° C. Five grams of ferric nitratenonahydrate is added over a period of four minutes to begin theexperiment. The iron salt distributes through the mixture but there isno visually apparent activity for a few minutes. The temperature of thereaction mixture slowly rises. About 10 minutes after the start of theiron addition, the mixture turns dark purple. Simultaneously, thereaction temperature peaks at 31° C. At this point, a timer is startedfor the taking of samples for Ferrate(VI) analysis. The water/ice bathmaintains a constant temperature of 19-20° C. Fraction Actual Re- Time,Actual Expected Observed of Iron action Temp- min Wt, g AbsorbanceAbsorbance in (VI) State erature, ° C.  2 0.30 0.95 0.37 0.39 29  6 0.391.24 0.66 0.53 26 10 0.31 0.98 0.55 0.56 23 15 0.32 1.02 0.64 0.63 22 250.30 0.95 0.64 0.67 — 35 0.29 0.92 0.66 0.72 — 45 0.33 1.05 0.76 0.72 —60 0.31 0.98 0.71 0.72 —

Example 8 Preparation of Ferrate(VI)

[0414] Ferrate is synthesized using the procedure of Example 1. 30 g ofNaOH plus 75 g of water were mixed in the reaction chamber, followed bythe addition of 6.5 g of Cl₂. Another 70 g of NaOH is added. Thesolution phase of this is reacted with 25 grams of ferric nitrate.Exper- Temp, Caustic, Chlorine, C vs. Agita- iment ° C. 1st/2nd g IronForm B‡ tion 1 30 30/25 13 25/60 Fe/H₂O C T fitting 2 30 30/10 13 25/60Fe/H₂O C T fitting 3 30 30/0 10 25/60 Fe/H₂O C T fitting 4 35 30/0 1025/60 Fe/H₂O C T fitting 5 40 30/0 10 25/60 Fe/H₂O C T fitting 6 35 15/07.5 25/60 Fe/H₂O C T fitting 7 30 30/25 13 25/60 Fe/H₂O B Blade 8 3030/10 13 25/60 Fe/H₂O B Blade 9 30 30/0 10 25/60 Fe/H₂O B Blade 10 3530/0 10 25/60 Fe/H₂O B Blade 11 40 30/0 10 25/60 Fe/H₂O B Blade 12 3515/0 7.5 25/60 Fe/H₂O B Blade 13 30 30/25 13 25/60 Fe/H₂O C Passive 1430 30/10 13 25/60 Fe/H₂O C Passive 15 30 30/0 10 25/60 Fe/H₂O C Passive16 35 30/0 10 25/60 Fe/H₂O C Passive 17 40 30/0 10 25/60 Fe/H₂O CPassive 18 35 15/0 7.5 25/60 Fe/H₂O C Passive 19 30 30/25 13 25/60basepm* C Passive 20 30 30/10 13 25/60 basepm C Passive 21 30 30/0 1025/60 basepm C Passive 22 35 30/0 10 25/60 basepm C Passive 23 40 30/010 25/60 basepm C Passive 24 35 15/0 7.5 25/60 basepm C Passive 25 3530/0 10 25/30 sol 1† C Passive 26 35 30/0 10 25/30 sol 2 C Passive 27 3530/0 10 25/30 sol 3 C Passive 28 35 30/0 10 25/30 sol 4 C Passive 29 3530/0 10 25/30 sol 5 C Passive 30 35 30/0 10 25/30 sol 6 C Passive

Example 9 Preparation of Ferrate(VI)

[0415] Ferrate is synthesized using the procedure of Example 1, except12.9 g of chlorine was used instead of 6.5 g and the second addition ofsodium hydroxide was 25 g instead of 70 g. Reaction vessel is a 30 mLbeaker in a 30° C. water bath. Begin with 15 g of hypochlorite/sodiumhydroxide solution. Over two minutes, add a proportionate amount offerric nitrate nonahydrate crystals (4.8 g). Begin pumping bleach intothe vessel at a rate of 1.2 g per minute. Simultaneously, continuouslyfeed iron crystals into the vessel at a rate of 0.24 g per minute. Stopafter 20 minutes, this point in time becomes time=0 in the table below.During this period the maximum temperature was 40° C. but mostly atemperature of close to 30° C. was maintained. After the additions werestopped samples were taken for spectrophotometric analysis. ActualFraction of Actual re- Time, weight, Expected Actual Iron in the actiontemp- min gm absorbance absorbance (VI) state erature, ° C.  0 0.32672.93 1.121 0.38 30.1 10 0.3284 2.94 1.294 0.44 28.8 20 0.3550 3.18 1.4660.46 28.2

Example 10 Literature Preparation of Ferrate(VI)

[0416] Ferrate was synthesized using a recipe given by Audette andQuail, Inorganic Chemistry 11(8) 1904 (1972). IC 11(8) 1904 (1972)Experimental Procedure Recipe Weight, grams Weight, Experimental On a 75grams Ingredient grams Moles Moles Procedure of water basis Water 75 1075 1st NaOH 30 0.10 4 30 Cl₂ (gas) 6.5 0.092 0.038 2.7 20.25 0.29 (75 gwater basis) 2nd NaOH 70 0.24 9.6 72 Ferric 25 0.062 0.005 2.02 15Nitrate Nonahy- drate

Example 11 Procedure for the Synthesis of Ferrate(VI)

[0417] Take a small sample bottle and record its tare weight to thenearest 0.01 grams. Inside a dry box, weigh 30 g of sodium hydroxideinto a 300 mL fleaker, 70 g of sodium hydroxide into a 150 mL fleaker,and 5.0 g of ferric nitrate nonahydrate into the sample bottle. Cap eachvessel. Take the three vessels out of the dry box. Re-weigh and recordthe weight of the small sample bottle to the nearest 0.01 grams. Add 75g of deionized water to the large fleaker. Re-cap the large fleaker andset it in ice.

[0418] Take the cap off the large fleaker, put a TEFLON coated stirringbar in it, weigh it and record the weight. Set the fleaker in a largecrystallizing dish on a stirring plate, add ice to the crystallizingdish to above the level of the solution, and start the stirring. Put aglass thermometer in the solution.

[0419] Clean and dry the delivery tip from a chlorine delivery system.Start the chlorine addition into the sodium hydroxide solution. Makesure the sodium hydroxide solution does not back up into the deliverytube toward the chlorine cylinder. Watch for the speed of bubbles anddon't go too fast. Watch the temperature and keep it below 20° C.Periodically check the weight of the fleaker plus contents and stop thechlorine addition when enough chlorine has been added (20 g of chlorinein this example). Record the weight of the fleaker plus contents.

[0420] Put the flask back in the ice bath with the thermometer. Slowlybegin adding the second aliquot of NaOH. Watch the temperature closely;it is preferably around 25° C. Filter the mixture through the frittedglass filter. Put forty grams of filtrate in a 50 mL beaker with a shortstirring bar. Put the beaker in the crystallizing dish and add water andice or heat as necessary to establish the temperature at the set point.Put a thermocouple in the reaction vessel.

[0421] Begin adding ferric nitrate nonahydrate crystals from the smallsample vial an simultaneously begin recording the temperature of thecontents of the reaction vessel. It will take four or five minutes toadd the ferric crystals. Once the purple color is strongly in evidence,begin taking samples for ferrate(VI) analysis.

Example 12 Preparation of Ferrate(VI)

[0422] Ferrate is synthesized using the procedure of Example 1, except23.1 g of chlorine was used instead of 6.5 g. 40 g of coarse glass fritfiltered bleach in saturated sodium hydroxide solution was added to a 50mL Pyrex beaker with a TEFLON® stirring bar. The beaker was placed in alarge crystallizing dish on a magnetic stirrer plate. The water bathmaintained a temperature of 26-27° C. 5 g of ferric nitrate nonahydratewas added over a period of three minutes to begin the experiment*.During this step, the mixture foamed up slightly causing the ironnitrate crystals to tend to float on the foam and not mix in. At sixminutes the mixture was a dark purple color and sampling was initiatedby taking about 0.3 g and diluting to 100 g with cold buffer solution.Six minutes coincided with the peak mixture temperature, 42° C. Duringthe next few minutes, the foam continued to rise. Actual Fraction ofActual Re- Time, Wt, Expected Observed Iron in action Temp- min* gmAbsorbance Absorbance (VI) State erature, ° C.  6 0.31 0.97 0.14 0.14 42 8 0.33 1.03 0.25 0.24 35 10 0.31 0.97 0.24 0.25 31 16 0.31 0.97 0.270.28 27.5 22 0.34 1.06 0.30 0.28 31 0.32 1.00 0.29 0.29 46 0.32 1.000.30 0.29

Example 13 Preparation of Ferrate(VI)

[0423] Ferrate is synthesized using the procedure of Example 1, except12 g of chlorine was used instead of 6.5 g. Reaction vessel is ajacketed beaker maintained at 35° C. Begin with 20 g ofhypochlorite/sodium. Gradually add 1.6 g of ferric nitrate nonahydratecrystals. This is a 5 fold stoichiometric excess of hypochlorite overferric(III). The maximum temperature achieved during this step was 39°C. Actual Fraction of Actual re- Time, weight, Expected Actual Iron inthe action temp- min gm absorbance absorbance (VI) state erature, ° C.15 0.3233 1.36 0.86 0.63 35.2 30 0.3427 1.44 1.14 0.79 35.2 45 0.29841.26 1.10 0.87 35.2 60 0.3289 1.39 1.25 0.90 35.2

Example 14 Loop Reactor Procedure

[0424] A jacketed mixing vessel set to control the temperature at 30° C.is used. A reactor vessel in the form of a tube is used with acontrolled temperature setting of 35° C. A multi-head variable speedperistaltic pump set to deliver sodium hypochlorite solution to themixing chamber at a speed of approximately 30 mg/sec is used. Anothertube on the pump head is used to transfer mixture from the mixingchamber to the reactor tube.

[0425] Prepare a sample vial with more than 10 g of ferric nitratenonahydrate, record its weight. Prepare another sample vial with ferricnitrate nonahydrate to deliver 3.42 g. Add 17.1 grams of sodiumhypochlorite solution to the mixing chamber. Begin the mixing. Graduallyadd 3.42 g of ferric nitrate nonahydrate. Begin timing the experimentand begin delivering sodium hypochlorite solution from the peristalticpump. At one minute intervals, add 0.342 grams of crystals (measuredvisually) into the mixing chamber. After the 5 minute add, begintransferring reaction mixture to the loop by positioning the inlet ofthe peristaltic pump transfer tube at the surface of the reactionmixture. After the 10, 15 and 20 minute add, record the weight of thecrystal vial. After the 20 minute add, stop delivering sodiumhypochlorite solution and stop adding crystals. Re-position the inlet tothe peristaltic pump transfer tube to near the bottom of the mixingvessel and continue pumping from there to the Loop reactor. When theMixing Chamber is empty, stop the peristaltic pump. At 60 minutes, get asample of the product from the outlet end of the loop reactor andmeasure its absorbance. At 80 minutes, get a sample of the product fromthe inlet end of the loop reactor and measure its absorbance.

Example 15 Preparation of Ferrate(VI)

[0426] Ferrate is synthesized using the procedure of Example 1. 40 g ofcoarse glass frit filtered bleach in saturated sodium hydroxide solutionis added to a 50 mL Pyrex beaker with a TEFLON® stirring bar. The beakeris placed in a large crystallizing dish on a magnetic stirrer plate. Thecrystallizing dish has a water/ice mixture to maintain a temperature of19-20° C. 5 g of ferric nitrate nonahydrate is added over a period offour minutes to begin the experiment. The iron salt distributes throughthe mixture but there is no visually apparent activity for a fewminutes. The temperature of the reaction mixture does slowly elevate.Relatively suddenly, the mixture turns dark purple. This happened 10minutes after the start of the iron addition, simultaneously, thereaction temperature peaked at 31° C. At this point, a timer is startedfor the taking of samples for Ferrate(VI) analysis. The water/ice bathmaintained a constant temperature of 19-20° C. Actual Fraction ofReaction Time, Actual Expected Observed Iron in Temperature, min Wt, gmAbsorbance Absorbance (VI) State ° C.  2 0.30 0.95 0.37 0.39 29  6 0.391.24 0.66 0.53 26 10 0.31 0.98 0.55 0.56 23 15 0.32 1.02 0.64 0.63 22 250.30 0.95 0.64 0.67 — 35 0.29 0.92 0.66 0.72 — 45 0.33 1.05 0.76 0.72 —60 0.31 0.98 0.71 0.72 —

Example 16 Preparation of Ferrate(VI)

[0427] 40 grams of coarse glass frit filtered bleach solution is addedto a 50 mL jacketed reaction vessel with a TEFLON® stirring bar.Controlled temperature water is circulated through the jacket to controland establish the reaction temperature. Five grams of ferric nitratenonahydrate is added over a period of a few minutes to begin theexperiment. Time, Actual Expected Observed Fraction of Iron ActualReaction min Wt, gm Absorbance Absorbance in (VI) State Temperature, °C. Notes Temp control point 30° C. 0 22.4 Begin iron addition 2 27Complete iron addition 2.5 30 3.5 33.9 Beginning of reaction noted 50.33 1.04 0.25 0.24 31.1 10 0.32 1.01 0.40 0.40 30.7 17 0.31 0.98 0.480.49 30.4 25 0.33 1.04 0.59 0.57 30.4 35 0.32 1.01 0.60 0.59 30.3 450.34 1.08 0.695 0.64 30.5 Temp control point 35° C. 0 24 Begin ironaddition 2 28.6 Complete iron addition 2.5 32 3.5 37 Beginning ofreaction noted 5 0.32 0.285 1.01 0.28 36 10 0.34 0.52 1.08 0.48 35.4 170.34 0.61 1.08 0.56 35.3 25 0.34 0.67 1.08 0.62 35.3 35 0.31 0.68 0.980.69 35.3 45 0.34 0.813 1.08 0.75 35.3 60 0.43 1.11 1.36 0.82 35.2

Example 17 Preparation of Ferrate(VI)

[0428] Reaction vessel is a 30 mL beaker in a 30° C. water bath. Beginwith 15 g of hypochlorite/sodium hydroxide solution. Over two minutes,add a stoichiometric amount of ferric nitrate nonahydrate crystals (3g). Begin pumping bleach into the vessel at a rate of 1.2 g per minute.Simultaneously, continuously feed iron crystals into the vessel at arate of 0.24g per minute. Stop after 20 minutes, this point in timebecomes time=0 in the table below. During this period the maximumtemperature was 40° C. but mostly a temperature of close to 30° C. wasmaintained. After the additions were stopped samples were taken forspectrophotometric analysis. Actual reaction Actual Expected Fraction ofIron in the temperature, Time, min weight, gm absorbance Actualabsorbance (VI) state ° C.  0 0.3267 2.93 1.121 0.38 30.1 10 0.3284 2.941.294 0.44 28.8 20 0.3550 3.18 1.466 0.46 28.2

Conclusion

[0429] Thus, those of skill in the art will appreciate that the methods,devices, and uses herein provide a relatively easy and economical way ofproducing ferrate in close proximity to the site of use.

[0430] One skilled in the art will appreciate that these methods anddevices are and may be adapted to carry out the objects and obtain theends and advantages mentioned, as well as those inherent therein. Themethods, procedures, and devices described herein are presentlyrepresentative of preferred embodiments and are exemplary and are notintended as limitations on the scope of the invention. Changes thereinand other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the claims.

[0431] It will be apparent to one skilled in the art that varyingsubstitutions and modifications may be made to the invention disclosedherein without departing from the scope and spirit of the invention.

[0432] Those skilled in the art recognize that the aspects andembodiments of the invention set forth herein may be practiced separatefrom each other or in conjunction with each other. Therefore,combinations of separate embodiments are within the scope of theinvention as claimed herein.

[0433] All patents and publications mentioned in the specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

[0434] The invention illustratively described herein suitably may bepracticed in the absence of any element or elements, limitation orlimitations which is not specifically disclosed herein. Thus, forexample, in each instance herein any of the terms “comprising”,“consisting essentially of” and “consisting of” may be replaced witheither of the other two terms. The terms and expressions which have beenemployed are used as terms of description and not of limitation, andthere is no intention that in the use of such terms and expressionsindicates the exclusion of equivalents of the features shown anddescribed or portions thereof. It is recognized that variousmodifications are possible within the scope of the invention claimed.Thus, it should be understood that although the present invention hasbeen specifically disclosed by preferred embodiments and optionalfeatures, modification and variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims.

[0435] In addition, where features or aspects of the invention aredescribed in terms of Markush groups, those skilled in the art willrecognize that the invention is also thereby described in terms of anyindividual member or subgroup of members of the Markush group. Forexample, if X is described as selected from the group consisting ofbromine, chlorine, and iodine, claims for X being bromine and claims forX being bromine and chlorine are fully described.

[0436] Other embodiments are within the following claims.

What is claimed is:
 1. A method of continuously synthesizing ferrate,comprising: a) mixing an iron salt and an oxidizing agent in a mixingchamber to provide a mixture; b) delivering at least a portion of themixture to a reaction chamber; c) continuously generating ferrate in thereaction chamber; d) delivering at least a portion of the ferrate to asite of use that is proximal to the reaction chamber; and e) addingadditional iron salt and oxidizing agent to the mixing chamber.
 2. Themethod of claim 1, further comprising adding a base to the mixture. 3.The method of claim 1, additionally comprising repeating steps (b)through (d).
 4. A method of treating, at a site of use, a mixture havingat least one impurity, comprising a) continuously generating ferrate ina reaction chamber located proximal to the site of use; b) contactingthe ferrate with the mixture at the site of use, whereby at least aportion of the impurity is oxidized.
 5. A method of treating, at a siteof use, a mixture having at least one impurity, comprising a)continuously generating ferrate in a reaction chamber located proximalto the site of use; b) contacting the ferrate with the mixture at thesite of use, whereby at least a portion of the impurity is coagulated.6. The method of claim 4, wherein the step of continuously generatingferrate comprises the steps of: a) mixing an iron salt and an oxidizingagent in a mixing chamber to provide a mixture; b) delivering at least aportion of the mixture to a reaction chamber; c) continuously generatingferrate in the reaction chamber; d) delivering at least a portion of theferrate to a site of use that is proximal to the reaction chamber; ande) adding additional iron salt and oxidizing agent to the mixingchamber.
 7. The method of claim 6, further comprising adding a base tothe mixture.
 8. The method of claim 5, wherein the step of continuouslygenerating ferrate comprises the steps of: a) mixing an iron salt and anoxidizing agent in a mixing chamber to provide a mixture; b) deliveringat least a portion of the mixture to a reaction chamber; c) continuouslygenerating ferrate in the reaction chamber; d) delivering at least aportion of the ferrate to a site of use that is proximal to the reactionchamber; and e) adding additional iron salt and oxidizing agent to themixing chamber.
 9. The method of claim 8, further comprising adding abase to the mixture.
 10. A device for continuously synthesizing ferratefor delivery to a site of use, comprising: a) a first holding chamber;b) a second holding chamber; c) a mixing chamber controllably connectedto the first holding chamber and to the second holding chamber, intowhich a content of the first holding chamber and a content of a secondholding chamber are added to form a first mixture; d) a reaction chambercontrollably connected to the mixing chamber, the reaction chamberadapted to receive the first mixture and maintain the first mixture fora period of time; e) a ferrate mixture in the reaction chamber; and f)an output opening in the reaction chamber through which the ferratemixture is adapted to be transported to the site of use, wherein thesite of use is proximal to the reaction chamber.
 11. The device of claim10, wherein the mixing chamber further comprises a temperature controldevice.
 12. A method of purifying drinking water comprising contactingferrate generated by the method of claim 1 with the drinking water,wherein the contacting is at a site proximal to the generation site. 13.A method of purifying waste water comprising contacting ferrategenerated by the method of claim 1 with the waste water, wherein thecontacting is at a site proximal to the generation site.
 14. A method ofpurifying sewage comprising contacting ferrate generated by the methodof claim 1 with the sewage, wherein the contacting is at a site proximalto the generation site.
 15. A method of continuously synthesizingferrate, comprising: a) providing a mixture of an iron salt and anoxidizing agent; b) continuously delivering at least a portion of themixture to a heating chamber; c) exposing the mixture to elevatedtemperatures in the heating chamber, thereby generating ferrate; d)removing at least a portion of the ferrate generated in step c) from theheating chamber; e) adding additional mixture to the heating chamber.16. A device for continuously synthesizing ferrate, comprising: a) aholding chamber; b) a mover controllably connected to the holdingchamber such that at least a portion of a content of the holding chamberis transferred to the mover; c) a heating chamber, through which atleast a portion of the mover moves; d) an output opening in the heatingchamber through which the content on the mover is adapted to betransported to a site of use, wherein the site of use is proximal to theheating chamber.
 17. The device of claim 16, wherein the heating chamberfurther comprises a temperature control device.
 18. A device forcontinuously synthesizing ferrate, comprising: a) a reaction chambercomprising two electrodes and a solution of an iron salt, wherein theelectrodes provide sufficient electric current to convert the solutionof an iron salt to a solution of ferrate; b) a holding chambercontrollably connected to the reaction chamber, into which the solutionof ferrate is kept for a period of time; and c) an output opening in theholding chamber through which the mixture is adapted to be transportedto a site of use, wherein the site of use is proximal to the holdingchamber.
 19. A method of continuously synthesizing ferrate, comprising:a) continuously providing an aqueous solution comprising an iron salt ina reaction chamber, wherein the mixing chamber comprises at least twoelectrodes; b) providing sufficient electric current to the at least twoelectrodes to convert at least a portion of the iron salt to ferrate; c)delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and d) adding additional aqueoussolution to the reaction chamber.
 20. The method of claim 19, furthercomprising adding a base to the aqueous solution.
 21. A method ofsynthesizing ferrate, comprising: a) mixing an aqueous solutioncomprising an iron salt and an oxidizing agent in a mixing chamber toform a solution of ferrate; b) delivering at least a portion of thesolution of ferrate to a site of use that is proximal to the mixingchamber.